Polymers of ethylene oxide and carbon dioxide

ABSTRACT

The present disclosure is directed, in part, to methods of synthesizing a poly(ethylene carbonate) polymer from the reaction of ethylene oxide (EO) and carbon dioxide (CO 2 ) in the presence of a metal complex. The present disclosure also provides novel metal complexes. In one aspect, the metal complex is of the formula (I), wherein R 1 , R 2 , R 3 , M, X and Ring A are as defined herein.

PRIORITY CLAIM

This application claims priority to U.S. Provisional Patent ApplicationSer. No. 61/052,061, filed May 9, 2008. The entire contents of thispriority application are incorporated herein by reference.

BACKGROUND

Poly(ethylene carbonate) (PEC) is a flexible, biocompatible, andbiodegradable material with high gas barrier properties, particularlyfor O₂. It is made via the ring opening polymerization of ethylenecarbonate (EC) or by the copolymerization of ethylene oxide (EO) andCO₂. Ring opening polymerization of EC initiated by KOH or Sn(OAc)₂ athigh temperature leads to poly(ethylene oxide-co-ether carbonate) ratherthan PEC. The high reaction temperatures required for this route causethe elimination of CO₂ during polymerization. The alternatingcopolymerization of epoxides and CO₂ to form polycarbonates wasoriginally discovered by Inoue in 1969. Since then, numerous catalystsystems have been developed for epoxide/CO₂ copolymerization (see, forexample, Coates and Moore, Angew. Chem. Int. Ed. 2004, 43, 6618-6639;Super and Beckman, Trends Polym. Sci. 1997, 5, 236-240; Darensbourg, andHoltcamp, Coord. Chem. Rev. 1996, 153, 155-174). Various systems forEO/CO₂ copolymerization based on Zn, Al, or double metal cyanide specieshave been reported; however, they require high CO₂ pressure and sufferfrom low catalytic activities.

SUMMARY

The present disclosure provides, in part, methods of synthesizingpoly(ethylene carbonate) polymers from the reaction of ethylene oxide(EO) and carbon dioxide (CO₂) in the presence of a metal complex. Thepresent disclosure also provides novel metal complexes. In particular,the inventors have found that N,N′-bis(salicydene)-1,2-cyclohexyldiamine(salcy) metal complexes are effective in this polymerization reaction,and particularly in providing poly(ethylene carbonate) polymers with lowether content.

In one aspect, the metal complexes as described herein are of theformula (I):

wherein:

M is a metal selected from zinc, cobalt, chromium, aluminum, titanium,ruthenium or manganese;

X is absent or is a nucleophilic ligand;

each instance of R¹, R², and R³ is, independently, selected fromhydrogen, halogen, optionally substituted aliphatic, optionallysubstituted heteroaliphatic, optionally substituted aryl, and optionallysubstituted heteroaryl, or R¹ and R², or R² and R³, are joined to forman optionally substituted aryl or optionally substituted heteroarylring; and

Ring A forms an optionally substituted 5- to 6-membered ring.

In another aspect, the present disclosure provides a method ofsynthesizing a poly(ethylene carbonate) polymer, wherein the polymer ismade up of Y, and optionally Z, and wherein the percentage of Y isgreater than the percentage of Z,

the method comprising reacting ethylene oxide and carbon dioxide in thepresence of a metal complex.

In certain embodiments, the above method comprises a metal complex offormula (I), as described above and herein.

This application refers to various issued patent, published patentapplications, journal articles, and other publications, all of which areincorporated herein by reference.

The details of one or more embodiments are set forth herein.

DEFINITIONS

Definitions of specific functional groups and chemical terms aredescribed in more detail below. For purposes of this disclosure, thechemical elements are identified in accordance with the Periodic Tableof the Elements, CAS version, Handbook of Chemistry and Physics, 75^(th)Ed., inside cover, and specific functional groups are generally definedas described therein. Additionally, general principles of organicchemistry, as well as specific functional moieties and reactivity, aredescribed in Organic Chemistry, Thomas Sorrell, University ScienceBooks, Sausalito, 1999; Smith and March March's Advanced OrganicChemistry, 5^(th) Edition, John Wiley & Sons, Inc., New York, 2001;Larock, Comprehensive Organic Transformations, VCH Publishers, Inc., NewYork, 1989; Carruthers, Some Modern Methods of Organic Synthesis, 3^(rd)Edition, Cambridge University Press, Cambridge, 1987; the entirecontents of each of which are incorporated herein by reference.

Certain compounds of the present disclosure can comprise one or moreasymmetric centers, and thus can exist in various isomeric forms, e.g.,stereoisomers and/or diastereomers. Thus, inventive compounds andcompositions thereof may be in the form of an individual enantiomer,diastereomer or geometric isomer, or may be in the form of a mixture ofstereoisomers. In certain embodiments, the compounds of the disclosureare enantiopure compounds. In certain other embodiments, mixtures ofstereoisomers or diastereomers are provided.

Furthermore, certain compounds, as described herein may have one or moredouble bonds that can exist as either the Z or E isomer, unlessotherwise indicated.

The disclosure additionally encompasses the compounds as individualisomers substantially free of other isomers and alternatively, asmixtures of various isomers, e.g., racemic mixtures of stereoisomers. Inaddition to the above-mentioned compounds per se, this disclosure alsoencompasses pharmaceutically acceptable derivatives of these compoundsand compositions comprising one or more compounds.

Where a particular enantiomer is preferred, it may, in some embodimentsbe provided substantially free of the opposite enantiomer, and may alsobe referred to as “optically enriched.” “Optically-enriched,” as usedherein, means that the compound is made up of a significantly greaterproportion of one enantiomer. In certain embodiments the compound ismade up of at least about 90% by weight of a preferred enantiomer. Inother embodiments the compound is made up of at least about 95%, 98%, or99% by weight of a preferred enantiomer. Preferred enantiomers may beisolated from racemic mixtures by any method known to those skilled inthe art, including chiral high pressure liquid chromatography (HPLC) andthe formation and crystallization of chiral salts or prepared byasymmetric syntheses. See, for example, Jacques, et al., Enantiomers,Racemates and Resolutions (Wiley Interscience, New York, 1981); Wilen,S. H., et al., Tetrahedron 33:2725 (1977); Eliel, E. L. Stereochemistryof Carbon Compounds (McGraw-Hill, NY, 1962); Wilen, S. H. Tables ofResolving Agents and Optical Resolutions p. 268 (E. L. Eliel, Ed., Univ.of Notre Dame Press, Notre Dame, Ind. 1972).

The terms “halo” and “halogen” as used herein refer to an atom selectedfrom fluorine (fluoro, —F), chlorine (chloro, —Cl), bromine (bromo,—Br), and iodine (iodo, —I).

The term “aliphatic” or “aliphatic group”, as used herein, denotes ahydrocarbon moiety that may be straight-chain (i.e., unbranched),branched, or cyclic (including fused, bridging, and spiro-fusedpolycyclic) and may be completely saturated or may contain one or moreunits of unsaturation, but which is not aromatic. Unless otherwisespecified, aliphatic groups contain 1-12 carbon atoms. In certainembodiments, aliphatic groups contain 1-8 carbon atoms. In certainembodiments, aliphatic groups contain 1-6 carbon atoms. In someembodiments, aliphatic groups contain 1-5 carbon atoms, in someembodiments, aliphatic groups contain 1-4 carbon atoms, in yet otherembodiments aliphatic groups contain 1-3 carbon atoms, and in yet otherembodiments aliphatic groups contain 1-2 carbon atoms. Suitablealiphatic groups include, but are not limited to, linear or branched,alkyl, alkenyl, and alkynyl groups, and hybrids thereof such as(cycloalkyl)alkyl, (cycloalkenyl)alkyl or (cycloalkyl)alkenyl.

The term “unsaturated”, as used herein, means that a moiety has one ormore double or triple bonds.

The terms “cycloaliphatic”, “carbocycle”, or “carbocyclic”, used aloneor as part of a larger moiety, refer to a saturated or partiallyunsaturated cyclic aliphatic monocyclic or bicyclic ring systems, asdescribed herein, having from 3 to 12 members, wherein the aliphaticring system is optionally substituted as defined above and describedherein. Cycloaliphatic groups include, without limitation, cyclopropyl,cyclobutyl, cyclopentyl, cyclopentenyl, cyclohexyl, cyclohexenyl,cycloheptyl, cycloheptenyl, cyclooctyl, cyclooctenyl, andcyclooctadienyl. In some embodiments, the cycloalkyl has 3-6 carbons.The terms “cycloaliphatic”, “carbocycle” or “carbocyclic” also includealiphatic rings that are fused to one or more aromatic or nonaromaticrings, such as decahydronaphthyl or tetrahydronaphthyl, where theradical or point of attachment is on the aliphatic ring.

The term “alkyl,” as used herein, refers to saturated, straight- orbranched-chain hydrocarbon radicals derived from an aliphatic moietycontaining between one and six carbon atoms by removal of a singlehydrogen atom. Unless otherwise specified, alkyl groups contain 1-12carbon atoms. In certain embodiments, alkyl groups contain 1-8 carbonatoms. In certain embodiments, alkyl groups contain 1-6 carbon atoms. Insome embodiments, alkyl groups contain 1-5 carbon atoms, in someembodiments, alkyl groups contain 1-4 carbon atoms, in yet otherembodiments alkyl groups contain 1-3 carbon atoms, and in yet otherembodiments alkyl groups contain 1-2 carbon atoms. Examples of alkylradicals include, but are not limited to, methyl, ethyl, n-propyl,isopropyl, n-butyl, iso-butyl, sec-butyl, sec-pentyl, iso-pentyl,tert-butyl, n-pentyl, neopentyl, n-hexyl, sec-hexyl, n-heptyl, n-octyl,n-decyl, n-undecyl, dodecyl, and the like.

The term “alkenyl,” as used herein, denotes a monovalent group derivedfrom a straight- or branched-chain aliphatic moiety having at least onecarbon-carbon double bond by the removal of a single hydrogen atom.Unless otherwise specified, alkenyl groups contain 2-12 carbon atoms. Incertain embodiments, alkenyl groups contain 2-8 carbon atoms. In certainembodiments, alkenyl groups contain 2-6 carbon atoms. In someembodiments, alkenyl groups contain 2-5 carbon atoms, in someembodiments, alkenyl groups contain 2-4 carbon atoms, in yet otherembodiments alkenyl groups contain 2-3 carbon atoms, and in yet otherembodiments alkenyl groups contain 2 carbon atoms. Alkenyl groupsinclude, for example, ethenyl, propenyl, butenyl, 1-methyl-2-buten-1-yl,and the like.

The term “alkynyl,” as used herein, refers to a monovalent group derivedfrom a straight- or branched-chain aliphatic moiety having at least onecarbon-carbon triple bond by the removal of a single hydrogen atom.Unless otherwise specified, alkynyl groups contain 2-12 carbon atoms. Incertain embodiments, alkynyl groups contain 2-8 carbon atoms. In certainembodiments, alkynyl groups contain 2-6 carbon atoms. In someembodiments, alkynyl groups contain 2-5 carbon atoms, in someembodiments, alkynyl groups contain 2-4 carbon atoms, in yet otherembodiments alkynyl groups contain 2-3 carbon atoms, and in yet otherembodiments alkynyl groups contain 2 carbon atoms. Representativealkynyl groups include, but are not limited to, ethynyl, 2-propynyl(propargyl), 1-propynyl, and the like.

The term “aryl” used alone or as part of a larger moiety as in“aralkyl”, “aralkoxy”, or “aryloxyalkyl”, refers to monocyclic andpolycyclic ring systems having a total of five to 20 ring members,wherein at least one ring in the system is aromatic and wherein eachring in the system contains three to twelve ring members. The term“aryl” may be used interchangeably with the term “aryl ring”. In certainembodiments of the present disclosure, “aryl” refers to an aromatic ringsystem which includes, but is not limited to, phenyl, biphenyl,naphthyl, anthracyl and the like, which may bear one or moresubstituents. Also included within the scope of the term “aryl”, as itis used herein, is a group in which an aromatic ring is fused to one ormore additional rings, such as benzofuranyl, indanyl, phthalimidyl,naphthimidyl, phenantriidinyl, or tetrahydronaphthyl, and the like.

The terms “heteroaryl” and “heteroar-”, used alone or as part of alarger moiety, e.g., “heteroaralkyl”, or “heteroaralkoxy”, refer togroups having 5 to 14 ring atoms, preferably 5, 6, or 9 ring atoms;having 6, 10, or 14 π electrons shared in a cyclic array; and having, inaddition to carbon atoms, from one to five heteroatoms. The term“heteroatom” refers to nitrogen, oxygen, or sulfur, and includes anyoxidized form of nitrogen or sulfur, and any quaternized form of a basicnitrogen. Heteroaryl groups include, without limitation, thienyl,furanyl, pyrrolyl, imidazolyl, pyrazolyl, triazolyl, tetrazolyl,oxazolyl, isoxazolyl, oxadiazolyl, thiazolyl, isothiazolyl,thiadiazolyl, pyridyl, pyridazinyl, pyrimidinyl, pyrazinyl, indolizinyl,purinyl, naphthyridinyl, benzofuranyl and pteridinyl. The terms“heteroaryl” and “heteroar-”, as used herein, also include groups inwhich a heteroaromatic ring is fused to one or more aryl,cycloaliphatic, or heterocyclyl rings, where the radical or point ofattachment is on the heteroaromatic ring. Nonlimiting examples includeindolyl, isoindolyl, benzothienyl, benzofuranyl, dibenzofuranyl,indazolyl, benzimidazolyl, benzthiazolyl, quinolyl, isoquinolyl,cinnolinyl, phthalazinyl, quinazolinyl, quinoxalinyl, 4H-quinolizinyl,carbazolyl, acridinyl, phenazinyl, phenothiazinyl, phenoxazinyl,tetrahydroquinolinyl, tetrahydroisoquinolinyl, andpyrido[2,3-b]-1,4-oxazin-3(4H)-one. A heteroaryl group may be mono- orbicyclic. The term “heteroaryl” may be used interchangeably with theterms “heteroaryl ring”, “heteroaryl group”, or “heteroaromatic”, any ofwhich terms include rings that are optionally substituted. The term“heteroaralkyl” refers to an alkyl group substituted by a heteroaryl,wherein the alkyl and heteroaryl portions independently are optionallysubstituted.

As used herein, the terms “heterocycle”, “heterocyclyl”, “heterocyclicradical”, and “heterocyclic ring” are used interchangeably and refer toa stable 5- to 7-membered monocyclic or 7-14-membered bicyclicheterocyclic moiety that is either saturated or partially unsaturated,and having, in addition to carbon atoms, one or more, preferably one tofour, heteroatoms, as defined above. When used in reference to a ringatom of a heterocycle, the term “nitrogen” includes a substitutednitrogen. As an example, in a saturated or partially unsaturated ringhaving 0-3 heteroatoms selected from oxygen, sulfur or nitrogen, thenitrogen may be N (as in 3,4-dihydro-2H-pyrrolyl), NH (as inpyrrolidinyl), or ⁺NR (as in N-substituted pyrrolidinyl).

A heterocyclic ring can be attached to its pendant group at anyheteroatom or carbon atom that results in a stable structure and any ofthe ring atoms can be optionally substituted. Examples of such saturatedor partially unsaturated heterocyclic radicals include, withoutlimitation, tetrahydrofuranyl, tetrahydrothienyl, pyrrolidinyl,pyrrolidonyl, piperidinyl, pyrrolinyl, tetrahydroquinolinyl,tetrahydroisoquinolinyl, decahydroquinolinyl, oxazolidinyl, piperazinyl,dioxanyl, dioxolanyl, diazepinyl, oxazepinyl, thiazepinyl, morpholinyl,and quinuclidinyl. The terms “heterocycle”, “heterocyclyl”,“heterocyclyl ring”, “heterocyclic group”, “heterocyclic moiety”, and“heterocyclic radical”, are used interchangeably herein, and alsoinclude groups in which a heterocyclyl ring is fused to one or morearyl, heteroaryl, or cycloaliphatic rings, such as indolinyl,3H-indolyl, chromanyl, phenanthridinyl, or tetrahydroquinolinyl, wherethe radical or point of attachment is on the heterocyclyl ring. Aheterocyclyl group may be mono- or bicyclic. The term“heterocyclylalkyl” refers to an alkyl group substituted by aheterocyclyl, wherein the alkyl and heterocyclyl portions independentlyare optionally substituted.

As used herein, the term “partially unsaturated” refers to a ring moietythat includes at least one double or triple bond. The term “partiallyunsaturated” is intended to encompass rings having multiple sites ofunsaturation, but is not intended to include aryl or heteroarylmoieties, as herein defined.

As described herein, compounds of the disclosure may contain “optionallysubstituted” moieties. In general, the term “substituted”, whetherpreceded by the term “optionally” or not, means that one or morehydrogens of the designated moiety are replaced with a suitablesubstituent. Unless otherwise indicated, an “optionally substituted”group may have a suitable substituent at each substitutable position ofthe group, and when more than one position in any given structure may besubstituted with more than one substituent selected from a specifiedgroup, the substituent may be either the same or different at everyposition. Combinations of substituents envisioned by this disclosure arepreferably those that result in the formation of stable or chemicallyfeasible compounds. The term “stable”, as used herein, refers tocompounds that are not substantially altered when subjected toconditions to allow for their production, detection, and, in certainembodiments, their recovery, purification, and use for one or more ofthe purposes disclosed herein.

Suitable monovalent substituents on a substitutable carbon atom of an“optionally substituted” group are independently halogen;—(CH₂)₀₋₄R^(o); —(CH₂)₀₋₄OR^(o); —O—(CH₂)₀₋₄C(O)OR^(o);—(CH₂)₀₋₄CH(OR^(o))₂; —(CH₂)₀₋₄SR^(o); —(CH₂)₀₋₄Ph, which may besubstituted with R^(o); —(CH₂)₀₋₄O(CH₂)₀₋₁Ph which may be substitutedwith R^(o); —CH═CHPh, which may be substituted with R^(o); —NO₂; —CN;—N₃; —(CH₂)₀₋₄N(R^(o))₂; —(CH₂)₀₋₄N(R^(o))C(O)R^(o); —N(R^(o))C(S)R^(o);—(CH₂)₀₋₄N(R^(o))C(O)NR^(o) ₂; —N(R^(o))C(S)NR^(o) ₂;—(CH₂)₀₋₄N(R^(o)C(O)OR^(o); —N(R^(o)N(R^(o)C(O)R^(o);—N(R^(o))N(R^(o))C(O)NR^(o) ₂; —N(R^(o))N(R^(o)C(O)OR^(o);—(CH₂)₀₋₄C(O)R^(o); —C(S)R^(o); —(CH₂)₀₋₄C(O)OR^(o);—(CH₂)₀₋₄C(O)N(R^(o))₂; —(CH₂)₀₋₄C(O)SR^(o); —(CH₂)₀₋₄C(O)OSiR^(o) ₃;—(CH₂)₀₋₄OC(O)R^(o); —OC(O)(CH₂)₀₋₄SR—, SC(S)SR^(o);—(CH₂)₀₋₄SC(O)R^(o); —(CH₂)₀₋₄C(O)NR^(o) ₂; —C(S)NR^(o) ₂; —C(S)SR^(o);—SC(S)SR^(o), —(CH₂)₀₋₄OC(O)NR^(o) ₂; —C(O)N(OR^(o))R^(o);—C(O)C(O)R^(o); —C(O)CH₂C(O)R^(o); —C(NOR^(o))R^(o); —(CH₂)₀₋₄S SR^(o);—(CH₂)₀₋₄S(O)₂R^(o); —(CH₂)₀₋₄S(O)₂OR^(o); —(CH₂)₀₋₄OS(O)₂R^(o);—S(O)₂NR^(o) ₂; —(CH₂)₀₋₄S(O)R^(o); —N(R^(o))S(O)₂NR^(o) ₂;—N(R^(o))S(O)₂R^(o); —N(OR^(o)R^(o); —C(NH)NR^(o) ₂; —P(O)₂R^(o);—P(O)RO₂; —OP(O)RO₂; —OP(O)(OR^(o) ₂; SiR^(o) ₃; —(C₁₋₄ straight orbranched)alkylene)O—N(R^(o))₂; or —(C₁₋₄ straight orbranched)alkylene)C(O)O—N(R^(o))₂, wherein each R^(o) may be substitutedas defined below and is independently hydrogen, C₁₋₈ aliphatic, —CH₂Ph,—O(CH₂)₀₋₁Ph, or a 5-6-membered saturated, partially unsaturated, oraryl ring having 0-4 heteroatoms independently selected from nitrogen,oxygen, or sulfur, or, notwithstanding the definition above, twoindependent occurrences of R^(o), taken together with their interveningatom(s), form a 3-12-membered saturated, partially unsaturated, or arylmono- or polycyclic ring having 0-4 heteroatoms independently selectedfrom nitrogen, oxygen, or sulfur, which may be substituted as definedbelow.

Suitable monovalent substituents on R^(o) (or the ring formed by takingtwo independent occurrences of R^(o) together with their interveningatoms), are independently halogen, —(CH₂)₀₋₂R^(), -(haloR^()),—(CH₂)₀₋₂OH, —(CH₂)₀₋₂OR^(), —(CH₂)₀₋₂CH(OR^())₂; —O(haloR*), —CN,—N₃, —(CH₂)₀₋₂C(O)R^(), —(CH₂)₀₋₂C(O)OH, —(CH₂)₀₋₂C(O)OR^(),—(CH₂)₀₋₄C(O)N(R^(o))₂; —(CH₂)₀₋₂SR^(), —(CH₂)₀₋₂SH, —(CH₂)₀₋₂NH₂,—(CH₂)₀₋₂NHR^(), —(CH₂)₀₋₂NR^() ₂, —NO₂, —SiR^() ₃, —OSiR^() ₃,—C(O)SR^(), —(C₁₋₄ straight or branched alkylene)C(O)OR^(), or—SSR^() wherein each R^() is unsubstituted or where preceded by “halo”is substituted only with one or more halogens, and is independentlyselected from C₁₋₄ aliphatic, —CH₂Ph, —O(CH₂)₀₋₁Ph, or a 5-6-memberedsaturated, partially unsaturated, or aryl ring having 0-4 heteroatomsindependently selected from nitrogen, oxygen, or sulfur. Suitabledivalent substituents on a saturated carbon atom of R^(o) include ═O and═S.

Suitable divalent substituents on a saturated carbon atom of an“optionally substituted” group include the following: ═O, ═S, ═NNR*₂,═NNHC(O)R*, ═NNHC(O)OR*, ═NNHS(O)₂R*, ═NR*, ═NOR*, —O(C(R*₂))₂₋₃O—, or—S(C(R*₂))₂₋₃S—, wherein each independent occurrence of R* is selectedfrom hydrogen, C₁₋₆ aliphatic which may be substituted as defined below,or an unsubstituted 5-6-membered saturated, partially unsaturated, oraryl ring having 0-4 heteroatoms independently selected from nitrogen,oxygen, or sulfur. Suitable divalent substituents that are bound tovicinal substitutable carbons of an “optionally substituted” groupinclude: —O(CR*₂)₂₋₃O—, wherein each independent occurrence of R* isselected from hydrogen, C₁₋₆ aliphatic which may be substituted asdefined below, or an unsubstituted 5-6-membered saturated, partiallyunsaturated, or aryl ring having 0-4 heteroatoms independently selectedfrom nitrogen, oxygen, or sulfur.

Suitable substituents on the aliphatic group of R* include halogen,—R^(), —(haloR^()), —OH, —OR^(), —O(haloR^()), —CN, —C(O)OH,—C(O)OR^(), —NH₂, —NHR^(), —NR^() ₂, or —NO₂, wherein each R^() isunsubstituted or where preceded by “halo” is substituted only with oneor more halogens, and is independently C₁₋₄ aliphatic, —CH₂Ph,—O(CH₂)₀₋₁Ph, or a 5-6-membered saturated, partially unsaturated, oraryl ring having 0-4 heteroatoms independently selected from nitrogen,oxygen, or sulfur.

Suitable substituents on a substitutable nitrogen of an “optionallysubstituted” group include —R^(†), —NR^(†) ₂, —C(O)R^(†), —C(O)OR^(†),—C(O)C(O)R^(†), —C(O)CH₂C(O)R^(†), —S(O)₂R^(†), —S(O)₂NR^(†) ₂,—C(S)NR^(†) ₂, —C(NH)NR^(†) ₂, or —N(R^(†))S(O)₂R^(†); wherein eachR^(†) is independently hydrogen, C₁₋₆ aliphatic which may be substitutedas defined below, unsubstituted —OPh, or an unsubstituted 5-6-memberedsaturated, partially unsaturated, or aryl ring having 0-4 heteroatomsindependently selected from nitrogen, oxygen, or sulfur, or,notwithstanding the definition above, two independent occurrences ofR^(†), taken together with their intervening atom(s) form anunsubstituted 3-12-membered saturated, partially unsaturated, or arylmono- or bicyclic ring having 0-4 heteroatoms independently selectedfrom nitrogen, oxygen, or sulfur. A substitutable nitrogen may besubstituted with three R^(†) substituents to provide a charged ammoniummoiety —N⁺(R^(†))₃, wherein the ammonium moiety is further complexedwith a suitable counterion.

Suitable substituents on the aliphatic group of R^(†) are independentlyhalogen, —R^(), -(haloR^()), —OH, —OR^(), —O(haloR^()), —CN,—C(O)OH, —C(O)OR^(), —NH₂, —NHR^(), —NR^() ₂, or —NO₂, wherein eachR^() is unsubstituted or where preceded by “halo” is substituted onlywith one or more halogens, and is independently C₁₋₄ aliphatic, —CH₂Ph,—O(CH₂)₀₋₁Ph, or a 5-6-membered saturated, partially unsaturated, oraryl ring having 0-4 heteroatoms independently selected from nitrogen,oxygen, or sulfur.

As used herein, the term “tautomer” includes two or moreinterconvertable compounds resulting from at least one formal migrationof a hydrogen atom and at least one change in valency (e.g., a singlebond to a double bond, a triple bond to a single bond, or vice versa).The exact ratio of the tautomers depends on several factors, includingtemperature, solvent, and pH. Tautomerizations (i.e., the reactionproviding a tautomeric pair) may catalyzed by acid or base. Exemplarytautomerizations include keto-to-enol; amide-to-imide; lactam-to-lactim;enamine-to-imine; and enamine-to-(a different) enamine tautomerizations.

As used herein, the term “isomers” includes any and all geometricisomers and stereoisomers. For example, “isomers” include cis- andtrans-isomers, E- and Z-isomers, R- and S-enantiomers, diastereomers,(D)-isomers, (L)-isomers, racemic mixtures thereof, and other mixturesthereof, as falling within the scope of the disclosure. For instance, anisomer/enantiomer may, in some embodiments, be provided substantiallyfree of the corresponding enantiomer, and may also be referred to as“optically enriched.” “Optically-enriched,” as used herein, means thatthe compound is made up of a significantly greater proportion of oneenantiomer. In certain embodiments the compound of the presentdisclosure is made up of at least about 90% by weight of a preferredenantiomer. In other embodiments the compound is made up of at leastabout 95%, 98%, or 99% by weight of a preferred enantiomer. Preferredenantiomers may be isolated from racemic mixtures by any method known tothose skilled in the art, including chiral high pressure liquidchromatography (HPLC) and the formation and crystallization of chiralsalts or prepared by asymmetric syntheses. See, for example, Jacques, etal., Enantiomers, Racemates and Resolutions (Wiley Interscience, NewYork, 1981); Wilen, S. H., et al., Tetrahedron 33:2725 (1977); Eliel, E.L. Stereochemistry of Carbon Compounds (McGraw-Hill, NY, 1962); Wilen,S. H. Tables of Resolving Agents and Optical Resolutions p. 268 (E. L.Eliel, Ed., Univ. of Notre Dame Press, Notre Dame, Ind. 1972).

As used herein, “polymorph” refers to a crystalline inventive compoundexisting in more than one crystalline form/structure. When polymorphismexists as a result of difference in crystal packing it is called packingpolymorphism. Polymorphism can also result from the existence ofdifferent conformers of the same molecule in conformationalpolymorphism. In pseudopolymorphism the different crystal types are theresult of hydration or solvation.

BRIEF DESCRIPTION OF THE FIGURES

FIGS. 1A-1B. ¹H NMR spectra (300 MHz) of PEC obtained by catalyst 1(FIG. 1A) and 4 (FIG. 1B) in conjunction with [PPN]Cl.

FIG. 2. ¹H NMR spectra of PEC and PEO.

FIG. 3. (Salcy)CoOBzF₅ induced ethylene oxide (EO) polymerization in thepresence of PPNCl. The catalytic activity is strongly dependant on thePPNCl/Co ratio.

FIGS. 4A-4B. TGA (FIG. 4A) and DSC (FIG. 4B) analyses of PEO-b-PEC.

DETAILED DESCRIPTION OF CERTAIN EMBODIMENTS

As generally described above, the present disclosure provides methods ofsynthesizing poly(ethylene carbonate) compositions from ethylene oxideand carbon dioxide in the presence of a metal complex. In certainembodiments, the poly(ethylene carbonate) polymer is an alternatingpolymer. In certain embodiments, the poly(ethylene carbonate) polymer isa tapered co-polymer of polyethylene oxide and polyethylene carbonate.In certain embodiments, the poly(ethylene carbonate) polymer is a blockco-polymer of polyethylene oxide and polyethylene carbonate.

As is generally understood from the description as provided herein,poly(ethylene carbonate) polymers of the present disclosure encompasspoly(ethylene carbonate) (PEC), as well as polymers which comprisepoly(ethylene carbonate), such as, for example, polyethyleneoxide-co-polyethylene carbonate.

The present disclosure also provides novel metal complexes of theformula (I) as is described in detail below.

I. Metal Complexes

In certain embodiments, the metal complex is of the formula (I):

wherein:

M is a metal selected from zinc, cobalt, chromium, aluminum, titanium,ruthenium and manganese;

X is absent or is a nucleophilic ligand;

each instance of R¹, R², and R³ is, independently, selected fromhydrogen, halogen, optionally substituted aliphatic, optionallysubstituted heteroaliphatic, optionally substituted aryl, and optionallysubstituted heteroaryl, or R¹ and R², or R² and R³, are joined to forman optionally substituted aryl or optionally substituted heteroarylring; and

Ring A forms an optionally substituted 5- to 6-membered ring.

In certain embodiments, the metal is aluminum. In certain embodiments,the metal is chromium. In certain embodiments, the metal is zinc. Incertain embodiments, the metal is titanium. In certain embodiments, themetal is ruthenium. In certain embodiments, the metal is manganese. Incertain embodiments, the metal is cobalt. In certain embodiments,wherein the metal is cobalt, the cobalt has a valency of +3 (i.e.,Co(III)).

In certain embodiments, the metal complex is a metal catalyst.

In certain embodiments, X is absent. However, in certain embodiments, Xis a nucleophilic ligand. Exemplary nucleophilic ligands include, butare not limited to, —OR^(x), —SR^(X), —O(C═O)R^(x), —O(C═O)OR^(x),—O(C═O)N(R^(x))₂, —N(R^(x))(C═O)R^(x), —NC, —CN, halo (e.g., —Br, —I,—Cl), —N₃, —O(SO₂)R^(x) and —OPR^(x) ₃, wherein each R^(x) is,independently, selected from hydrogen, optionally substituted aliphatic,optionally substituted heteroaliphatic, optionally substituted aryl andoptionally substituted heteroaryl.

In certain embodiments, X is —O(C═O)R^(x), wherein R^(x) is selectedfrom optionally substituted aliphatic, fluorinated aliphatic, optionallysubstituted heteroaliphatic, optionally substituted aryl, fluorinatedaryl, and optionally substituted heteroaryl.

For example, in certain embodiments, X is —O(C═O)R^(x), wherein R^(x) isoptionally substituted aliphatic. In certain embodiments, X is—O(C═O)R^(x), wherein R^(x) is optionally substituted alkyl andfluoroalkyl. In certain embodiments, X is —O(C═O)CH₃ or —O(C═O)CF₃.

Furthermore, in certain embodiments, X is —O(C═O)R^(x), wherein R^(x) isoptionally substituted aryl, fluoroaryl, or heteroaryl. In certainembodiments, X is —O(C═O)R^(x), wherein R^(x) is optionally substitutedaryl. In certain embodiments, X is —O(C═O)R^(x), wherein R^(x) isoptionally substituted phenyl. In certain embodiments, X is —O(C═O)C₆H₅or —O(C═O)C₆F₅.

In certain embodiments, X is —OR^(x), wherein R^(x) is selected fromoptionally substituted aliphatic, optionally substitutedheteroaliphatic, optionally substituted aryl, and optionally substitutedheteroaryl.

For example, in certain embodiments, X is —OR^(x), wherein R^(x) isoptionally substituted aryl. In certain embodiments, X is —OR^(x),wherein R^(x) is optionally substituted phenyl. In certain embodiments,X is —OC₆H₅ or —OC₆H₂(2,4-NO₂).

In certain embodiments, X is halo. In certain embodiments, X is —Br. Incertain embodiments, X is —Cl. In certain embodiments, X is —I.

In certain embodiments, X is —O(SO₂)R^(x). In certain embodiments X is—OTs. In certain embodiments X is —OSO₂Me, In certain embodiments X is—OSO₂CF₃.

In certain embodiments, X is —N₃.

In certain embodiments, X is —NC

In certain embodiments, X is —CN.

In certain embodiments, Ring A forms an optionally substituted5-membered ring. In certain embodiments, Ring A forms an optionallysubstituted cyclopentyl ring. In certain embodiments, Ring A forms anoptionally substituted 5-membered aryl ring.

In certain embodiments, Ring A forms an optionally substituted6-membered ring. In certain embodiments, Ring A forms an optionallysubstituted cyclohexyl ring. In certain embodiments, Ring A forms anoptionally substituted 6-membered aryl ring.

II. Northern and Southern Hemisphere of the Metal Complex

The metal complex of formula (I) may be considered in two portions: aNorthern Hemisphere comprising the imine nitrogen atoms and Ring A, andSouthern Hemisphere, comprising the rest of the metal complex.

Northern Hemisphere

As generally understood from the above, the Northern Hemisphere of themetal complex is of the formula (i-a):

wherein Ring A forms an optionally substituted 5- to 6-membered ring.

In certain embodiments, Ring A forms an optionally substituted6-membered ring of the formula (i-b):

wherein R^(4A), R^(4B), R^(5A), R^(5B), and R^(6A), R^(6B) are,independently, selected from hydrogen, halogen, optionally substitutedaliphatic, optionally substituted heteroaliphatic, optionallysubstituted aryl, optionally substituted heteroaryl, and/or, R^(4A) andR^(4B), and/or R^(5A) and R^(5B), and/or and R^(6A) and R^(6B) areoptionally joined to form an oxo (═O) group, an oxime (═NOR^(a)) group,an imine (═NN(R^(a))₂) group, an alkenyl (═C(R^(b))₂) group, and/or a 3-to 6-membered spirocyclic ring, wherein each instance of R^(a) and R^(b)is, independently, hydrogen or optionally substituted aliphatic, whereinoptionally two R^(a) groups or two R^(b) groups are joined to form a 3-to 6-membered ring.

In certain embodiments, R^(4A), R^(4B), R^(5A), R^(5B), R^(6A), andR^(6B) are, independently, selected from hydrogen, optionallysubstituted aliphatic, optionally substituted heteroaliphatic,optionally substituted aryl, and optionally substituted heteroaryl. Incertain embodiments, R^(4A), R^(4B), R^(5A), R^(5B), R^(6A), and R^(6B)are, independently, selected from hydrogen and optionally substitutedaliphatic. In certain embodiments, R^(4A), R^(4B), R^(5A), R^(5B),R^(6A), and R^(6B) are, independently, selected from hydrogen andoptionally substituted heteroaliphatic. In certain embodiments, R^(4A),R^(4B), R^(5A), R^(5B), R^(6A), and R^(6B) are independently, selectedfrom hydrogen and optionally substituted aryl. In certain embodiments,R^(4A), R^(4B), R^(5A), R^(5B), R^(6A), and R^(6B) are, independently,selected from hydrogen and optionally substituted heteroaryl. In certainembodiments, two or more of R^(4A), R^(4B), R^(5A), R^(5B), R^(6A), andR^(6B), are joined to form one or more aliphatic, heteroaliphatic,aromatic, or heteroaromatic rings having 3 to 8 total ring atoms.

In certain embodiments, each of R^(4A), R^(4B), R^(5A), R^(5B), R^(6A),and R^(6B) are hydrogen.

For example, in certain embodiments of formula (i-b), wherein each ofR^(4A), R^(4B), R^(5A), R^(5B), R^(6A), and R^(6B) are hydrogen, Ring Aforms a 6-membered ring of the formula:

In certain embodiments, Ring A forms an optionally substituted6-membered ring of the formula (i-c):

wherein R^(5A) and R^(5B) are, independently, selected from hydrogen,halogen, optionally substituted aliphatic, optionally substitutedheteroaliphatic, optionally substituted aryl, optionally substitutedheteroaryl, and/or, R^(5A) and R^(5B) are optionally joined to form anoxo (═O) group, an oxime (═NOR^(a)) group, an imine (═NN(R^(a))₂) group,an alkenyl (═C(R^(b))₂) group, and/or a 3- to 6-membered spirocyclicring, wherein each instance of R^(a) and R^(b) is, independently,hydrogen or optionally substituted aliphatic, wherein optionally twoR^(a) groups or two R^(b) groups are joined to form a 5- to 6-memberedring;

each instance of R¹² is selected from hydrogen, halogen, —OR^(c),—OC(═O)R^(c), —OC(═O)OR^(c), —OC(═O)N(R^(d))₂, —OSO₂R^(d), —C(═O)OR^(c),—C(═O)N(R^(d))₂, —CN, —CNO, —NCO, —N₃, —NO2, —N(Rd)2,—N(R^(d))C(═O)R^(c), —N(R^(d))C(═O)OR^(c), —N(R^(d))SO₂R^(d), —SO₂R^(d),—SOR^(d), —SO₂N(R^(d))₂, optionally substituted aliphatic, optionallysubstituted heteroaliphatic, optionally substituted aryl, optionallysubstituted heteroaryl, wherein each instance of R^(c) is,independently, optionally substituted aliphatic, optionally substitutedheteroaliphatic, optionally substituted aryl, optionally substitutedheteroaryl, and each instance of R^(d) is, independently, hydrogen,optionally substituted aliphatic, optionally substitutedheteroaliphatic, optionally substituted aryl, optionally substitutedheteroaryl; and

c is 0 to 4.

In certain embodiments, R^(5A) and R^(5B) are, independently, selectedfrom hydrogen and optionally substituted aliphatic. In certainembodiments, R^(5A) and R^(5B) are, independently, selected fromhydrogen and optionally substituted heteroaliphatic. In certainembodiments, R^(5A) and R^(5B) are, independently, selected fromhydrogen and optionally substituted aryl. In certain embodiments, R^(5A)and R^(5B) are, independently, selected from hydrogen and optionallysubstituted heteroaryl.

However, in certain embodiments, each R^(5A) and R^(5B) is hydrogen.

In certain embodiments, c is 0 to 2. In certain embodiments, c is 0to 1. In certain embodiments, c is 0. In certain embodiments, c is 1.

In certain embodiments, each instance of R¹² is, independently, selectedfrom hydrogen and optionally substituted aliphatic. In certainembodiments, each instance of R¹² is, independently, selected fromhydrogen and optionally substituted heteroaliphatic. In certainembodiments, each instance of R¹² is, independently, selected fromhydrogen and optionally substituted aryl. In certain embodiments, eachinstance of R¹² is, independently, selected from hydrogen and optionallysubstituted heteroaryl.

However, in certain embodiments, each instance of R¹² is hydrogen.

In certain embodiments, Ring A forms an optionally substituted5-membered ring of the formula (I-d):

wherein R^(4A), R^(4B), R^(5A), and R^(5B) are, independently, selectedfrom hydrogen, halogen, optionally substituted aliphatic, optionallysubstituted heteroaliphatic, optionally substituted aryl, optionallysubstituted heteroaryl, and/or, R^(4A) and R^(4B) and/or R^(5A) andR^(5B) are optionally joined to form an oxo (═O) group, an oxime(═NOR^(a)) group, an imine (═NN(R^(a))₂) group, an alkenyl (═C(R^(b))₂)group, and/or a 3- to 6-membered spirocyclic ring, wherein each instanceof R^(a) and R^(b) is, independently, hydrogen or optionally substitutedaliphatic, wherein optionally two R^(a) groups or two R^(b) groups arejoined to form a 5- to 6-membered ring.

In certain embodiments, wherein R^(4A), R^(4B), R^(5A), and R^(5B) are,independently, selected from hydrogen, optionally substituted aliphatic,optionally substituted heteroaliphatic, optionally substituted aryl,optionally substituted heteroaryl, or wherein one of R^(4A), R^(4B),R^(5A), and R^(5B) and one of R^(4A), R^(4B), R^(5A), and R^(5B) areoptionally joined to form a 3- to 7-membered ring.

In certain embodiments, R^(4A), R^(4B), R^(5A), and R^(5B) are,independently, selected from hydrogen and optionally substitutedaliphatic. In certain embodiments, R^(4A), R^(4B), R^(5A), and R^(5B)are, independently, selected from hydrogen and optionally substitutedheteroaliphatic. In certain embodiments, R^(4A), R^(4B), R^(5A), andR^(5B) are, independently, selected from hydrogen and optionallysubstituted aryl. In certain embodiments, R^(4A), R^(4B), R^(5A), andR^(5B) are, independently, selected from hydrogen and optionallysubstituted heteroaryl. In certain embodiments, one of R^(4A), R^(4B),R^(5A), and R^(5B) and one of R^(4A), R^(4B), R^(5A), and R^(5B) areoptionally joined to form a 3- to 6-membered ring.

However, in certain embodiments, each instance of R^(4A), R^(4B),R^(5A), and R^(5B) is hydrogen.

For example, in certain embodiments of formula (I-d), wherein R^(4A),R^(4B), R^(5A), and R^(5B) are each hydrogen, Ring A forms a 5-memberedring of the formula:

In certain embodiments of formula (I-d), wherein R^(4B) and R^(5B) arejoined to form an optionally substituted 6-membered ring, Ring A formsan optionally substituted 5-membered ring of the formula (i-f):

R^(4A), R^(5A), R^(13A), R^(13B), R^(14A), R^(14B), R^(15A), R^(15B),R^(16A), R^(16B) are, independently, selected from hydrogen, halogen,—OR^(c), —OC(═O)R^(c), —OC(═O)OR^(c), —OC(═O)N(R^(d))₂, —OSO₂R^(d),—C(═O)OR^(c), —C(═O)N(R^(d))₂, —CN, —CNO, —NCO, —N₃, —NO2, —N(Rd)2,—N(R^(d))C(═O)OR^(c), —N(R^(d))C(═O)R^(c), —N(R^(d))SO₂R^(d), —SO₂R^(d),—SOR^(d), —SO₂N(R^(d))₂, optionally substituted aliphatic, optionallysubstituted heteroaliphatic, optionally substituted aryl, optionallysubstituted heteroaryl; and/or, optionally, R^(13A) and R^(13B), and/orR^(14A) and R^(14B), and/or R^(15A) and R^(15B), and/or R^(16A) andR^(16B) are optionally joined to form an oxo (═O) group, an oxime(═NOR^(a)) group, an imine (═NN(R^(a))₂) group, an alkenyl (═C(R^(b))₂)group, and/or a 3- to 6-membered spirocyclic ring, wherein each instanceof R^(a) and R^(b) is, independently, hydrogen or optionally substitutedaliphatic, wherein optionally two R^(a) groups or two R^(b) groups arejoined to form a 3- to 6-membered ring.

In certain embodiments, R^(4A), R^(5A), R^(13A), R^(13B), R^(14A),R^(14B), R^(15A), R^(15B), R^(16A), R^(16B) are, independently, selectedfrom hydrogen, halogen, optionally substituted aliphatic, optionallysubstituted heteroaliphatic, optionally substituted aryl, optionallysubstituted heteroaryl. In certain embodiments, R^(4A), R^(5A), R^(13A),R^(13B), R^(14A), R^(14B), R^(15A), R^(15B), R^(16A), R^(16B) areindependently, selected from hydrogen and optionally substitutedaliphatic. In certain embodiments, R^(4A), R^(5A), R^(13A), R^(13B),R^(14A), R^(14B), R^(15A), R^(15B), R^(16A), R^(16B) are, independently,selected from hydrogen and optionally substituted heteroaliphatic. Incertain embodiments, R^(4A), R^(5A), R^(13A), R^(13B), R^(14A), R^(14B),R^(15A), R^(15B), R^(16A), R^(16B) are, independently, selected fromhydrogen and optionally substituted aryl. In certain embodiments,R^(4A), R^(5A), R^(13A), R^(13B), R^(14A), R^(14B), R^(15A), R^(15B),R^(16A), R^(16B) are, independently, selected from hydrogen andoptionally substituted heteroaryl.

However, in certain embodiments, each of R^(4A), R^(5A), R^(13A),R^(13B), R^(14A), R^(14B), R^(15A), R^(15B), R^(16A), R^(16B) ishydrogen.

For example, in certain embodiments of formula (I-d), wherein R^(4B) andR^(5B) are joined to form an optionally substituted 6-membered ring andeach of R^(4A), R^(5A), R^(13A), R^(13B), R^(14A), R^(14B), R^(15A),R^(15B), R^(16A), R^(16B) is hydrogen, Ring A forms an optionallysubstituted 5-membered ring of the formula (i-g):

In certain embodiments of formula (I-d), wherein R^(4B) and R^(5B) arejoined to form an optionally substituted 6-membered ring, Ring A formsan optionally substituted 5-membered ring of any of the formulae (i-h)to (i-k):

or a mixture thereof;

wherein R^(4A), R^(5A), R^(13A), R^(13B), R^(14A), R^(14B), R^(15A),R^(15B), R^(16A), R^(16B) are, independently, selected from hydrogen,halogen, —OR^(c), —OC(═O)R^(c), —OC(═O)OR^(c), —OC(═O)N(R^(d))₂,—OSO₂R^(d), —C(═O)OR^(c), —C(═O)N(R^(d))₂, —CN, —CNO, —NCO, —N₃, —NO₂,—N(Rd)2, —N(R^(d))C(═O)OR^(c), —N(R^(d))C(═O)R^(c), —N(R^(d))SO₂R^(d),—SO₂R^(d), —SOR^(B), —SO₂N(R^(d))₂, optionally substituted aliphatic,optionally substituted heteroaliphatic, optionally substituted aryl,optionally substituted heteroaryl, and/or, R^(13A) and R^(13B), and/orR^(14A) and R^(14B), and/or R^(15A) and R^(15B), and/or R^(16A) andR^(16B) are optionally joined to form an oxo (═O) group, an oxime(═NOR^(a)) group, an imine (═NN(R^(a))₂) group, an alkenyl (═C(R^(b))₂)group, and/or a 3- to 6-membered spirocyclic ring, wherein each instanceof R^(a) and R^(b) is, independently, hydrogen or optionally substitutedaliphatic, wherein optionally two R^(a) groups or two R^(b) groups arejoined to form a 5- to 6-membered ring.

In certain embodiments of formulae (i-h) to (i-k), wherein R^(4B) andR^(5B) are joined to form an optionally substituted 6-membered ring, andR^(4A), R^(5A), R^(13A), R^(13B), R^(14A), R^(14B), R^(15A), R^(15B),R^(16A), R^(16B) are each hydrogen, Ring A forms an optionallysubstituted 5-membered ring of any of the formulae (i-l) to (i-o):

or any mixture thereof.

In certain embodiments of formula (I-d), wherein R^(4B) and R^(5B) arejoined to form an optionally substituted 6-membered ring, Ring A formsan optionally substituted 5-membered ring of the formula (i-p):

wherein each instance of R¹⁷ is, independently, selected from hydrogen,halogen, —OR^(c), —OC(═O)R^(c), —OC(═O)OR^(c), —OC(═O)N(R^(d))₂,—OSO₂R^(d), —C(═O)OR^(c), —C(═O)N(R^(d))₂, —CN, —CNO, —NCO, —N₃, —NO₂,—N(R^(d))₂, —N(R^(d))C(═O)OR^(c), —N(R^(d))C(═O)R^(c),—N(R^(d))SO₂R^(d), —SO₂R^(d), —SOR^(B), —SO₂N(R^(d))₂, optionallysubstituted aliphatic, optionally substituted heteroaliphatic,optionally substituted aryl, optionally substituted heteroaryl, whereineach instance of R^(c) is, independently, optionally substitutedaliphatic, optionally substituted heteroaliphatic, optionallysubstituted aryl, optionally substituted heteroaryl, and each instanceof R^(d) is, independently, hydrogen, optionally substituted aliphatic,optionally substituted heteroaliphatic, optionally substituted aryl,optionally substituted heteroaryl; and/or two R¹⁷ groups adjacent toeach other are joined to form an optionally substituted 5- to 6-memberedring; and

d is 0 to 4.

In certain embodiments, d is 0 to 2. In certain embodiments, d is 0to 1. In certain embodiments, d is 0. In certain embodiments, d is 1.

In certain embodiments, each instance of R¹⁷ is, independently, selectedfrom hydrogen, optionally substituted aliphatic, optionally substitutedheteroaliphatic, optionally substituted aryl, and optionally substitutedheteroaryl. In certain embodiments, each instance of R¹⁷ is,independently, selected from hydrogen and optionally substitutedaliphatic. In certain embodiments, each instance of R¹⁷ is,independently, selected from hydrogen and optionally substitutedheteroaliphatic. In certain embodiments, each instance of R¹⁷ is,independently, selected from hydrogen and optionally substituted aryl.In certain embodiments, each instance of R¹⁷ is, independently, selectedfrom hydrogen and optionally substituted heteroaryl.

However, in certain embodiments, each instance of R¹⁷ is hydrogen.

For example, in certain embodiments of formula (i-p), wherein R^(4B) andR^(5B) are joined to form an optionally substituted 6-membered ring,Ring A forms an optionally substituted 5-membered ring of the formula(i-q):

Southern Hemisphere

As generally understood from the above, the Southern Hemisphere of themetal complex is of the formula (ii-a):

wherein M and X are as defined above and herein, and

each instance of R¹, R², and R³ is, independently, selected fromhydrogen, halogen, —OR^(c), —OC(═O)R^(c), —OC(═O)OR^(c),—OC(═O)N(R^(d))₂, —OSO₂R^(d), —C(═O)OR^(c), —C(═O)N(R^(d))₂, —CN, —CNO,—NCO, —N₃, —NO₂, —N(R^(d))₂, —N(R^(d))C(═O)OR^(c), —N(R^(d))C(═O)R^(c),—N(R^(d))SO₂R^(d), —SO₂R^(d), —SOR^(B), —SO₂N(R^(d))₂, optionallysubstituted aliphatic, optionally substituted heteroaliphatic,optionally substituted aryl, and optionally substituted heteroaryl,and/or any of R¹ and R², and/or any of R² and R³, are joined to form anoptionally substituted aryl or optionally substituted heteroaryl ring.

In certain embodiments, R¹ is hydrogen, halogen, optionally substitutedaliphatic, optionally substituted heteroaliphatic, optionallysubstituted aryl, or optionally substituted heteroaryl. In certainembodiments, each instance of R¹ is hydrogen. In certain embodiments,each instance of R¹ is halogen. In certain embodiments, each instance ofR¹ is optionally substituted aliphatic. In certain embodiments, eachinstance of R¹ is optionally substituted heteroaliphatic. In certainembodiments, each instance of R¹ is optionally substituted aryl. Incertain embodiments, each instance of R¹ is optionally substitutedheteroaryl.

In certain embodiments, each instance of R² is hydrogen, halogen,optionally substituted aliphatic, optionally substitutedheteroaliphatic, optionally substituted aryl, or optionally substitutedheteroaryl. In certain embodiments, each instance of R² is hydrogen. Incertain embodiments, each instance of R² is halogen. In certainembodiments, each instance of R² is optionally substituted aliphatic. Incertain embodiments, each instance of R² is optionally substitutedheteroaliphatic. In certain embodiments, each instance of R² isoptionally substituted aryl. In certain embodiments, each instance of R²is optionally substituted heteroaryl.

In certain embodiments, each instance of R³ is hydrogen, halogen,optionally substituted aliphatic, optionally substitutedheteroaliphatic, optionally substituted aryl, or optionally substitutedheteroaryl. In certain embodiments, each instance of R³ is hydrogen. Incertain embodiments, each instance of R³ is halogen. In certainembodiments, each instance of R³ is optionally substituted aliphatic. Incertain embodiments, each instance of R³ is optionally substitutedheteroaliphatic. In certain embodiments, each instance of R³ isoptionally substituted aryl. In certain embodiments, each instance of R³is optionally substituted heteroaryl.

However, in certain embodiments, R¹ and R² are joined to form anoptionally substituted aryl or optionally substituted heteroaryl ring.In certain embodiments, R¹ and R² are joined to form an optionallysubstituted aryl ring. In certain embodiments, R¹ and R² are joined toform an optionally substituted heteroaryl ring.

In other embodiments, R² and R³ are joined to form an optionallysubstituted aryl or optionally substituted heteroaryl ring. In certainembodiments, R² and R³ are joined to form an optionally substituted arylring. In certain embodiments, R² and R³ are joined to form an optionallysubstituted heteroaryl ring.

In certain embodiments, each instance of R¹, R², and R³ is,independently, selected from hydrogen, optionally substituted aliphatic,and/or any of R¹ and R², and/or any of R² and R³, are joined to form anoptionally substituted aryl or optionally substituted heteroaryl ring.In certain embodiments, each instance of R¹, R², and R³ is,independently, selected from hydrogen and/or any of R¹ and R² are joinedto form an optionally substituted aryl or optionally substitutedheteroaryl ring. In certain embodiments, each instance of R¹, R², and R³is, independently, selected from hydrogen and/or any of R² and R³, arejoined to form an optionally substituted aryl or optionally substitutedheteroaryl ring.

In certain embodiments, each instance of R¹, R², and R³ is,independently, selected from hydrogen and optionally substitutedaliphatic. In certain embodiments, each instance of R¹, R², and R³ is,independently, selected from hydrogen and optionally substitutedheteroaliphatic. In certain embodiments, each instance of R¹, R², and R³is, independently, selected from hydrogen and optionally substitutedaryl. In certain embodiments, each instance of R¹, R², and R³ is,independently, selected from hydrogen and optionally substitutedheteroaryl.

However, in certain embodiments, each instance of R¹, R², and R³ ishydrogen. In certain embodiments, each instance of R¹ and R³ ishydrogen. In certain embodiments, each instance of R² and R³ ishydrogen. In certain embodiments, each instance of R¹ and R² ishydrogen. In certain embodiments, each instance of R¹ is hydrogen. Incertain embodiments, each instance of R² is hydrogen. In certainembodiments, each instance of R³ is hydrogen.

In certain embodiments, wherein R¹ is an optionally substituted arylmoiety, the Southern Hemisphere of the metal complex is of the formula(ii-b):

wherein M, X, R² and R³ are as defined above and herein;

each instance of R¹¹ is, independently, selected from hydrogen, halogen,—OR^(c), —OC(═O)R^(c), —OC(═O)OR^(c), —OC(═O)N(R^(d))₂, —OSO₂R^(d),—C(═O)OR^(c), —C(═O)N(R^(d))₂, —CN, —CNO, —NCO, —N₃, —NO₂, —N(R^(d))₂,—N(R^(d))C(═O)OR^(c), —N(R^(d))C(═O)R^(c), —N(R^(d))SO₂R^(d), —SO₂R^(d),—SOR^(d), —SO₂N(R^(d))₂, optionally substituted aliphatic, optionallysubstituted heteroaliphatic, optionally substituted aryl, optionallysubstituted heteroaryl, wherein each instance of R^(c) is,independently, optionally substituted aliphatic, optionally substitutedheteroaliphatic, optionally substituted aryl, optionally substitutedheteroaryl, and each instance of R^(d) is, independently, hydrogen,optionally substituted aliphatic, optionally substitutedheteroaliphatic, optionally substituted aryl, optionally substitutedheteroaryl; and/or two R¹¹ groups adjacent to each other are joined toform an optionally substituted 5- to 6-membered ring; and

b is 0 to 5.

In certain embodiments, b is 0 to 2. In certain embodiments, b is 0to 1. In certain embodiments, b is 0. In certain embodiments, b is 1.

In certain embodiments, each instance of R¹¹ is, independently, selectedfrom hydrogen, optionally substituted aliphatic, optionally substitutedheteroaliphatic, optionally substituted aryl, and optionally substitutedheteroaryl, and/or two R¹¹ groups adjacent to each other are joined toform an optionally substituted 5- to 6-membered ring. In certainembodiments, each instance of R¹¹ is, independently, selected fromhydrogen and optionally substituted aliphatic. In certain embodiments,each instance of R¹¹ is, independently, selected from hydrogen,optionally substituted heteroaliphatic. In certain embodiments, eachinstance of R¹¹ is, independently, selected from hydrogen, optionallysubstituted aryl. In certain embodiments, each instance of R¹¹ is,independently, selected from hydrogen, optionally substitutedheteroaryl.

However, in certain embodiments, each instance of R¹¹ is hydrogen.

In certain embodiments, wherein one of R¹ and R² are joined to form anoptionally substituted aryl ring, the Southern Hemisphere of the metalcomplex is of the formula (ii-c):

wherein M, X, R¹, R² and R³ are, as defined above and herein; and

R⁷, R⁸, R⁹, and R¹⁰, are, independently, selected from hydrogen,halogen, —OR^(c), —OC(═O)R^(c), —OC(═O)OR^(c), —OC(═O)N(R^(d))₂,—OSO₂R^(d), —C(═O)OR^(c), —C(═O)N(R^(d))₂, —CN, —CNO, —NCO, —N₃, —NO₂,—N(R^(d))₂, —N(R^(d))C(═O)OR^(c), —N(R^(d))C(═O)R^(c),—N(R^(d))SO₂R^(d), —SO₂R^(d), —SOR^(d), —SO₂N(R^(d))₂, optionallysubstituted aliphatic, optionally substituted heteroaliphatic,optionally substituted aryl, optionally substituted heteroaryl, whereineach instance of R^(c) is, independently, optionally substitutedaliphatic, optionally substituted heteroaliphatic, optionallysubstituted aryl, optionally substituted heteroaryl, and each instanceof R^(d) is, independently, hydrogen, optionally substituted aliphatic,optionally substituted heteroaliphatic, optionally substituted aryl,optionally substituted heteroaryl; and/or two groups selected from R⁷,R⁸, R⁹, and R¹⁰ adjacent to each other are joined to form an optionallysubstituted 5- to 6-membered ring.

In certain embodiments, R⁷, R⁸, R⁹, and R¹⁰ are, independently, selectedfrom hydrogen, optionally substituted aliphatic, optionally substitutedheteroaliphatic, optionally substituted aryl, and optionally substitutedheteroaryl, and/or two groups selected from R⁷, R⁸, R⁹, and R¹⁰ adjacentto each other are joined to form an optionally substituted 5- to7-membered ring. In certain embodiments, R⁷, R⁸, R⁹, and R¹⁰ are,independently, selected from hydrogen and optionally substitutedaliphatic. In certain embodiments, R⁷, R⁸, R⁹, and R¹⁰ are,independently, selected from hydrogen and optionally substitutedheteroaliphatic. In certain embodiments, R⁷, R⁸, R⁹, and R¹⁰ are,independently, selected from hydrogen and optionally substituted aryl.In certain embodiments, R⁷, R⁸, R⁹, and R¹⁰ are, independently, selectedfrom hydrogen and optionally substituted heteroaryl.

In certain embodiments, R⁷, R⁸, R⁹, and R¹⁰ are, independently, selectedfrom hydrogen and optionally substituted aryl. In certain embodiments,R⁷, R⁸, R⁹, and R¹⁰ are, independently, selected from hydrogen andoptionally substituted phenyl.

In certain embodiments, R⁷, R⁸, R⁹, and R¹⁰ are, independently, selectedfrom hydrogen and optionally substituted C₁₋₁₀ aliphatic. In certainembodiments, R⁷, R⁸, R⁹, and R¹⁰ are, independently, selected fromhydrogen and optionally substituted C₁₋₁₀ alkyl. In certain embodiments,R⁷, R⁸, R⁹, and R¹⁰ are, independently, selected from hydrogen andmethyl, trichloromethyl, trifluoromethyl, ethyl, n-propyl, isopropyl,t-butyl, sec-butyl, iso-butyl, n-pentyl, neopentyl, amyl, trityl,adamantyl, thexyl, benzyl and cumyl.

However, in certain embodiments, each of R⁷, R⁸, R⁹, and R¹⁰ arehydrogen. In certain embodiments, each of R⁸ and R¹⁰ are hydrogen. Incertain embodiments, R⁸ is hydrogen. In certain embodiments, R¹⁰ ishydrogen.

For example, in certain embodiments of the formula (ii-c), wherein R⁸and R¹⁰ are hydrogen, the Southern Hemisphere of the metal complex is ofthe formula (ii-d):

wherein M, X, R¹, R², R³, R⁷ and R⁹ are, as defined above and herein.

In certain embodiments, of the formula (ii-d), wherein both R¹ and R²groups are joined to form an optionally substituted aryl ring, theSouthern Hemisphere of the metal complex is of the formula (ii-dd):

wherein M, X, R³, R⁷ and R⁹ are, as defined above and herein.

In certain embodiments, each occurrence of R³ is, independently,selected from hydrogen, halogen, optionally substituted aliphatic,optionally substituted heteroaliphatic, optionally substituted aryl, andoptionally substituted heteroaryl. In certain embodiments, eachoccurrence of R³ is hydrogen.

In certain embodiments, each occurrence of R⁷ and R⁹ is independentlyselected from hydrogen, optionally substituted aliphatic, optionallysubstituted heteroaliphatic, optionally substituted aryl, and optionallysubstituted heteroaryl.

In certain embodiments, each occurrence of R⁷ and R⁹ is independentlyselected from hydrogen, optionally substituted aliphatic and optionallysubstituted aryl.

In certain embodiments, each occurrence of R⁷ is the same. In certainembodiments, each occurrence of R⁹ is the same. In certain embodiments,each occurrence of R⁷ is the same and each occurrence of R⁹ is the same.In certain embodiments, R⁷ and R⁹ are different.

In certain embodiments, each occurrence of R⁷ and R⁹ is independentlyselected from hydrogen and optionally substituted C₁₋₁₂ aliphatic. Incertain embodiments, each occurrence of R⁷ and R⁹ is independentlyselected from hydrogen and optionally substituted C₁₋₁₂ alkyl. Incertain embodiments, each occurrence of R⁷ and R⁹ is independentlyselected from hydrogen, methyl, trichloromethyl, trifluoromethyl, ethyl,n-propyl, isopropyl, t-butyl, sec-butyl, iso-butyl, n-pentyl, neopentyl,amyl, trityl, adamantyl, thexyl, benzyl and cumyl.

In some embodiments R⁷ is hydrogen. In some embodiments R⁷ is methyl. Insome embodiments R⁷ is trichloromethyl. In some embodiments R⁷ istrifluoromethyl. In some embodiments R⁷ is ethyl. In some embodiments R⁷is n-propyl. In some embodiments R⁷ is isopropyl. In some embodiments R⁷is t-butyl. In some embodiments R⁷ is sec-butyl. In some embodiments R⁷is iso-butyl. In some embodiments R⁷ is n-pentyl. In some embodiments R⁷is neopentyl. In some embodiments R⁷ is amyl. In some embodiments R⁷ istrityl. In some embodiments R⁷ is adamantyl. In some embodiments R⁷ isthexyl. In some embodiments R⁷ is benzyl. In some embodiments R⁷ iscumyl.

In some embodiments R⁹ is hydrogen. In some embodiments R⁹ is methyl. Insome embodiments R⁹ is trichloromethyl. In some embodiments R⁹ istrifluoromethyl. In some embodiments R⁹ is ethyl. In some embodiments R⁹is n-propyl. In some embodiments R⁹ is isopropyl. In some embodiments R⁹is t-butyl. In some embodiments R⁹ is sec-butyl. In some embodiments R⁹is iso-butyl. In some embodiments R⁹ is n-pentyl. In some embodiments R⁹is neopentyl. In some embodiments R⁹ is amyl. In some embodiments R⁹ istrityl. In some embodiments R⁹ is adamantyl. In some embodiments R⁹ isthexyl. In some embodiments R⁹ is benzyl. In some embodiments R⁹ iscumyl.

In certain embodiments, each occurrence of R⁷ and R⁹ is independentlyselected from hydrogen and optionally substituted aryl. In certainembodiments, each occurrence of R⁷ and R⁹ is independently selected fromhydrogen and optionally substituted phenyl.

Without wishing to be bound by any theory, it is believed that therelative sizes of the R⁷ and R⁹ groups influence the rate andselectivity of the polymerization reactions catalyzed by the metalcomplexes In certain embodiments it is advantageous for there to be adifference in the sizes of R⁷ and R⁹. In certain embodiments, the groupR⁷ is larger than the group R⁹. However, in certain embodiments, thegroup R⁹ is larger than the group R⁷.

The relative size of a group (e.g., in this instance, R⁷ to R⁹) can bedetermined from the van der Waals surface and/or molecular volume ascalculated for that group. For a single molecule (i.e., a molecule forwhich there is a path between any two atoms along covalent bonds), thevan der Waals surface is a closed surface, and hence, it containsvolume. This volume is called the molecular volume, or van der Waalsvolume, and is usually given in A³. The straightforward way ofcalculating molecular volume on the computer is by numericalintegration, i.e., by surrounding the van der Waals envelope with a gridof small bricks and summing up the bricks whose centers are within thevan der Waals envelope of the molecule (i.e., are within a van der Waalsradius from atom nucleus) (see, for example, Whitley, “Van der Waalssurface graphs and molecular shape,” Journal of Mathematical Chemistry(1998) 23:377-397).

The relative size of a group can also be measured from the “A-value” fora given group. The A-value is a measure of the effective size of a givengroup. The “A-value” refers to the conformational energies (−G⁰ values)as determined for a substituted cyclohexane and the relativeaxial-equatorial disposition of the substituent (see Table 1, providedbelow, and pages 695-697 of Eliel and Wilen, Chapter 11 entitled“Configuration and Confirmation of Cyclic Molecules” of Stereochemistryof Organic Compounds, John Wiley & Sons, Inc., New York: 1994,incorporated herein by reference). More detailed tabulations have beencompiled by Hirsch, “Table of Conformational Energies”, Top. Stereochem.(1967) 1:199; Jensen and Bushweller, “Conformational Preferences inCyclohexanes and Cyclohexenes”, Adv. Alicycl. Chem. (1971) 3:139; andSchnieder and Hoppen “Carbon-13 Nuclear Magnetic ResonanceSubstituent-induced Shieldings and Conformational Equilibria inCyclohexanes”, J. Org. Chem. (1978) 43:3866; the entirety of each ofwhich is incorporated herein by reference.

TABLE 1 Exemplary A - values -G⁰ value Group kcal/mol kJ/mol —H ~0 ~0 —D0.0006 0.025 —T 0.011 0.046 —F 0.25-0.42 1.05-1.75 —Cl 0.53-0.642.22-2.68 —Br 0.48-0.67 2.01-2.80 —I 0.47-0.61 1.97-2.55 —OtBu 0.75 3.14—OPh 0.65 2.72 —OC(═O)CH₃ 0.68-0.87 2.85-3.64 —OSi(CH₃)₃ 0.74 3.10 —NO₂1.1 4.8 —P(CH₃)₂ 1.5-1.6 6.3-6.7 —P(Ph)₂ 1.8 7.5 —C(═O)CH₃ 1.02-1.524.27-6.36 —C(═O)OCH₃ 1.2-1.3 5.0-5.4 —C(═O)OCH₂CH₃ 1.1-1.2 4.6-5.0 —CN0.2 0.84 —CCH 0.41-0.52 1.71-2.18 —CHCH₂ 1.49-1.68 6.23-7.0  —CH₃(—Me)1.74 7.28 —CH₂CH₃(—Et) 1.79 7.49 —CH(CH₃)₂(—iPr) 2.21 9.25—C(CH₃)₃(—tBu) 4.7-4.9 19.7-20.5 —CH₂Ph 1.68 7.03 —Ph 2.8 11.71—Si(CH₃)₃ 2.5 10.5 —C₆H₁₁ 2.2 9.2 —CF₃ 2.4-2.5 10.0-10.5

Thus, in certain embodiments, the molecular volume of group R⁷ is largerthan the molecular volume of group R⁹. In certain embodiments, themolecular volume of R⁷ is at least 1.2 times greater than the molecularvolume of R⁹. In certain embodiments, the molecular volume of R⁷ is atleast 1.5 times greater than the molecular volume of R⁹. In certainembodiments, the molecular volume of R⁷ is at least 1.8 times greaterthan the molecular volume of R⁹. In certain embodiments, the molecularvolume of R⁷ is at least 2 times greater than the molecular volume ofR⁹. In certain embodiments, the molecular volume of R⁷ is at least 2.5times greater than the molecular volume of R⁹. In certain embodiments,the molecular volume of R⁷ is at least 3 times greater than themolecular volume of R⁹.

However, in certain embodiments, the molecular volume of group R⁹ islarger than the molecular volume of group R⁷. In certain embodiments,the molecular volume of R⁹ is at least 1.2 times greater than themolecular volume of R⁷. In certain embodiments, the molecular volume ofR⁹ is at least 1.5 times greater than the molecular volume of R⁷. Incertain embodiments, the molecular volume of R⁹ is at least 1.8 timesgreater than the molecular volume of R⁷. In certain embodiments, themolecular volume of R⁹ is at least 2 times greater than the molecularvolume of R⁷. In certain embodiments, the molecular volume of R⁹ is atleast 2.5 times greater than the molecular volume of R⁷. In certainembodiments, the molecular volume of R⁹ is at least 3 times greater thanthe molecular volume of R⁷.

In certain embodiments, the molecular volume of R⁷ is greater than themolecular volume of R⁹. In certain embodiments, the A-value of R⁷ is atleast 1.2 times greater than the A value of R⁹. In certain embodiments,the A-value of R⁷ is at least 1.5 times greater than the A value of R⁹.In certain embodiments, the A-value of R⁷ is at least 1.8 times greaterthan the A value of R⁹. In certain embodiments, the A-value of R⁷ is atleast 2 times greater than the A value of R⁹. In certain embodiments,the A-value of R⁷ is at least 2.5 times greater than the A value of R⁹.In certain embodiments, the A-value of R⁷ is at least 3 times greaterthan the A value of R⁹.

However, in certain embodiments, the A-value of R⁹ is greater than theA-value of R⁷. In certain embodiments, the A-value of R⁹ is at least 1.2times greater than the A value of R⁷. In certain embodiments, theA-value of R⁹ is at least 1.5 times greater than the A value of R⁷. Incertain embodiments, the A-value of R⁹ is at least 1.8 times greaterthan the A value of R⁷. In certain embodiments, the A-value of R⁹ is atleast 2 times greater than the A value of R⁷. In certain embodiments,the A-value of R⁹ is at least 2.5 times greater than the A value of R⁷.In certain embodiments, the A-value of R⁹ is at least 3 times greaterthan the A value of R⁷.

In certain embodiments, the A-value of R⁷ is greater than about 2.5kcal/mol. In certain embodiments, the A-value of R⁷ is greater thanabout 3 kcal/mol. In certain embodiments, the A-value of R⁷ is greaterthan about 3.5 kcal/mol. In certain embodiments, the A-value of R⁷ isgreater than about 4 kcal/mol.

In certain embodiments, the A-value of R⁹ is greater than about 2.5kcal/mol. In certain embodiments, the A-value of R⁹ is greater thanabout 3 kcal/mol. In certain embodiments, the A-value of R⁹ is greaterthan about 3.5 kcal/mol. In certain embodiments, the A-value of R⁹ isgreater than about 4 kcal/mol.

In certain embodiments, the A-value of R⁹ is between about 0 to about2.5 kcal/mol. In certain embodiments, the A-value of R⁹ is between about0 to about 3 kcal/mol. In certain embodiments, the A-value of R⁹ isbetween about 0 to about 3.5 kcal/mol. In certain embodiments, theA-value of R⁹ is between about 0 to about 4 kcal/mol.

In certain embodiments, the A-value of R⁷ is between about 0 to about2.5 kcal/mol. In certain embodiments, the A-value of R⁷ is between about0 to about 3 kcal/mol. In certain embodiments, the A-value of R⁷ isbetween about 0 to about 3.5 kcal/mol. In certain embodiments, theA-value of R⁷ is between about 0 to about 4 kcal/mol.

In certain embodiments, the Southern Hemisphere of the metal complex isof the formula (ii-e):

wherein M, X, R¹, R², R³, R⁷, R⁸, R⁹, and R¹⁰ are, as defined above andherein.

In certain embodiments of formula (ii-e), wherein R³, R⁸ and R¹⁰ arehydrogen, the Southern Hemisphere of the metal complex is of the formula(ii-f):

wherein M, X, R⁷ and R⁹ are as defined above and herein.

In certain embodiments, M is a metal selected from cobalt and chromium.In certain embodiments, M is cobalt. In certain embodiments, M is cobalt(III).

In certain embodiments, R⁷ is not —C(CH₃)₂Ph. In certain embodiments, R⁷is not —[C(CH₃)₂CH₂CH₂N(Bu)₃]⁺. In certain embodiments, R⁷ is not—CH(CH₂CH₃)C₆H₅. In certain embodiments, R⁷ is not —C(CH₃)₂CH₂C(CH₃)₃.In certain embodiments, R⁷ is not —CH(C₆H₅)CHCH₂. In certainembodiments, R⁷ is not —C(CH₃)₂CH₂CH₃. In certain embodiments, R⁷ is not1-methyl-cyclohexyl. In certain embodiments, R⁷ is not cyclohexyl.

In certain embodiments, R⁹ is not —C(CH₃)₂C₆H₅. In certain embodiments,R⁹ is not —[C(CH₃)₂CH₂CH₂N(Bu)₃]⁺. In certain embodiments, R⁹ is not—C(CH₃)₂CH₂C(CH₃)₃. In certain embodiments, R⁹ is not —C(CH₃)₃. Incertain embodiments, R⁹ is not —C(CH₃)₂CH₂CH₃. In certain embodiments,R⁹ is not —CH₃. In certain embodiments, R⁹ is not hydrogen.

In some embodiments, when R⁷ is —C(CH₃)₂Ph, R⁹ is other than —C(CH₃)₂Ph.In some embodiments, when R⁷ is —[C(CH₃)₂CH₂CH₂N(Bu)₃]⁺, R⁹ is otherthan —[C(CH₃)₂CH₂CH₂N(Bu)₃]⁺. In some embodiments, when R⁷ is—CH(CH₂CH₃)C₆H₅, R⁹ is other than hydrogen. In some embodiments, when R⁷is —C(CH₃)₂CH₂C(CH₃)₃, R⁹ is other than —C(CH₃)₂CH₂C(CH₃)₃. In someembodiments, when R⁷ is —CH(C₆H₅)CHCH₂, R⁹ is other than —C(CH₃)₃. Insome embodiments, when R⁷ is —C(CH₃)₂CH₂CH₃, R⁹ is other than —C(CH₃)₃.In some embodiments, when R⁷ is —C(CH₃)₂CH₂CH₃, R⁹ is other than—C(CH₃)₂CH₂CH₃. In some embodiments, when R⁷ is 1-methyl-cyclohexyl, R⁹is other than —C(CH₃)₃. In some embodiments, when R⁷ is1-methyl-cyclohexyl, R⁹ is other than —C(CH₃)₂CH₂CH₃. In someembodiments, when R⁷ is cyclohexyl, R⁹ is other than —CH₃.

In certain embodiments, the Southern Hemisphere is not selected from:

wherein X is as defined above and herein.

Any of the above formulae (i-a) to (i-q) may be combined with any of theabove formulae (ii-a) to (ii-f) to provide novel metal complexes.

For example, in certain embodiments, the present disclosure provides ametal complex of the formula (I-a):

wherein M, X, R¹, R², R³, R^(4A), R^(4B), R^(5A), R^(5B), R^(6A), andR^(6B) are as defined above and herein.

In certain embodiments, the present disclosure provides a metal complexof the formula (I-b):

wherein M, X, R¹, R² and R³ are as defined above and herein.

In certain embodiments, the present disclosure provides a metal complexof the formula (I-c):

wherein M, X, R¹, R², R³, R^(5A), R^(5B), R¹² and c are as defined aboveand herein.

In certain embodiments, the present disclosure provides a metal complexof the formula (I-d):

wherein M, X, R¹, R², R³, R^(4A), R^(4B), R^(5A), and R^(5B) are asdefined above and herein.

In certain embodiments, the present disclosure provides a metal complexof the formula (I-e):

wherein M, X, R¹, R², R³, R^(4A), R^(5A), R^(13A), R^(13B), R^(14A),R^(14B), R^(15A), R^(15B), R^(16A), R^(16B) are as defined above andherein.

In certain embodiments, the present disclosure provides a metal complexof any one of the formulae (I-f) to (I-i):

or any mixture thereof;

wherein M, X, R¹, R², R³, R^(4A), R^(5A), R^(13A), R^(13B), R^(14A),R^(14B), R^(15A), R^(15B), R^(16A), R^(16B) are as defined above andherein.

Where a particular enantiomer is preferred, it may, in some embodimentsbe provided substantially free of the corresponding enantiomer, and mayalso be referred to as “optically enriched.” “Optically-enriched,” asused herein, means that the compound is made up of a significantlygreater proportion of one enantiomer. In certain embodiments thecompound is made up of at least about 90% by weight of a preferredenantiomer. In other embodiments the compound is made up of at leastabout 95%, 98%, or 99% by weight of a preferred enantiomer.

Thus, in certain embodiments, the present disclosure provides anoptically enriched metal complex of any one of the formulae (I-f) to(I-i). In certain embodiments, the present disclosure provides anoptically enriched metal complex of formula (I-f). In certainembodiments, the present disclosure provides an optically enriched metalcomplex of formula (I-g). In certain embodiments, the present disclosureprovides an optically enriched metal complex of formula (I-h). Incertain embodiments, the present disclosure provides an opticallyenriched metal complex of formula (I-i).

In certain embodiments, the present disclosure provides a metal complexof the formula (I-j):

wherein M, X, R¹, R² and R³ are as defined above and herein.

In certain embodiments, the present disclosure provides a metal complexof any one of the formulae (I-k) to (I-n):

or any mixture thereof;

wherein M, X, R¹, R² and R³ are as defined above and herein.

In certain embodiments, the present disclosure provides an opticallyenriched metal complex of any one of the formulae (I-k) to (I-n). Incertain embodiments, the present disclosure provides an opticallyenriched metal complex of formula (I-k). In certain embodiments, thepresent disclosure provides an optically enriched metal complex offormula (I-l). In certain embodiments, the present disclosure providesan optically enriched metal complex of formula (I-m). In certainembodiments, the present disclosure provides an optically enriched metalcomplex of formula (I-n).

In certain embodiments, the present disclosure provides a metal complexof the formula (I-o):

wherein d, M, X, R¹, R², R³ and R¹⁷ are as defined above and herein.

In certain embodiments, the present disclosure provides a metal complexof the formula (I-p):

wherein d, M, X, R¹, R² and R³ are as defined above and herein.

In certain embodiments, the present disclosure provides a metal complexof the formula (I-q):

wherein M, X, R¹, R², R³, R¹¹, R^(4A), R^(5A), R^(13A), R^(13B),R^(14A), R^(14B), R^(15A), R^(15B), R^(16A), R^(16B) are as definedabove and herein.

In certain embodiments, the present disclosure provides a metal complexof the formula (I-r):

wherein b, R¹¹, M and X are as defined above and herein.

In certain embodiments, the present disclosure provides a metal complexof the formula (I-s):

wherein b, d, M, X, R¹, R², R³, R¹¹ and R¹⁷ are as defined above andherein.

In certain embodiments, the present disclosure provides a metal complexof the formula (I-t):

wherein b, M, X, R¹, R², R³ and R¹¹ are as defined above and herein.

In certain embodiments, the present disclosure provides a metal complexof the formula (I-u):

wherein M, X, R¹, R², R³, R^(4A), R^(5A), R⁷, R⁸, R⁹, R¹⁰, R^(13A),R^(13B), R^(14A), R^(14B), R^(15A), R^(15B), R^(16A), R^(16B) are asdefined above and herein.

In certain embodiments, the present disclosure provides a metal complexof the formula (I-v):

wherein M, X, R¹, R², R³, R⁷, R⁸, R⁹ and R¹⁰ are as defined above andherein.

In certain embodiments, the present disclosure provides a metal complexof the formula (I-w):

wherein M, X, R¹, R², R³, R^(4A), R^(5A), R⁷, R⁹, R^(13A), R^(13B),R^(14A), R^(14B), R^(15A), R^(15B), R^(16A), R^(16B) are as definedabove and herein.

In certain embodiments, the present disclosure provides a metal complexof the formula (I-x):

wherein M, X, R¹, R², R³, R⁷ and R⁹ are as defined above and herein.

In certain embodiments, the present disclosure provides a metal complexof the formula (I-y):

wherein M, X, R^(4A), R^(5A), R⁷, R⁸, R⁹, R¹⁰, R^(13A), R^(13B),R^(14A), R^(14B), R^(15A), R^(15B), R^(16A), R^(16B) are as definedabove and herein.

In certain embodiments, the present disclosure provides a metal complexof the formula (I-z):

wherein M, X, R^(4A), R^(5A), R⁷, R⁹, R^(13A), R^(13B), R^(14A),R^(14B), R^(15A), R^(15B), R^(16A), R^(16B) are as defined above andherein.

In certain embodiments, the present disclosure provides a metal complexof the formula (I-aa):

wherein M, X, R⁷ and R⁹ are as defined above and herein.

In certain embodiments, the present disclosure provides a metal complexof the formulae (I-bb) to (I-ee):

or any mixture thereof.

In certain embodiments, the present disclosure provides an opticallyenriched metal complex of any one of the formulae (I-bb) to (I-ee). Incertain embodiments, the present disclosure provides an opticallyenriched metal complex of formula (I-bb). In certain embodiments, thepresent disclosure provides an optically enriched metal complex offormula (I-cc). In certain embodiments, the present disclosure providesan optically enriched metal complex of formula (I-dd). In certainembodiments, the present disclosure provides an optically enriched metalcomplex of formula (I-ee).

In certain embodiments, the present disclosure provides a metal complexof the formula (I-ff):

wherein d, M, X, R¹, R², R³, R^(4A), R^(5A), R⁷, R⁸, R⁹, R¹⁰ and R¹⁷ areas defined above and herein.

In certain embodiments, the present disclosure provides a metal complexof the formula (I-gg):

wherein M, X, R¹, R², R³, R⁷, R⁸, R⁹ and R¹⁰ are as defined above andherein.

In certain embodiments, the present disclosure provides a metal complexof the formula (I-hh):

wherein d, M, X, R¹, R², R³, R⁷, R⁹ and R¹⁷ are as defined above andherein.

In certain embodiments, the present disclosure provides a metal complexof the formula (I-ii):

wherein M, X, R¹, R², R³, R⁷ and R⁹ are as defined above and herein.

In certain embodiments, the present disclosure provides a metal complexof the formula (I-jj):

wherein d, M, X, R^(4A), R^(5A), R⁷, R⁸, R⁹, R¹⁰ and R¹⁷ are as definedabove and herein.

In certain embodiments, the present disclosure provides a metal complexof the formula (I-kk):

wherein d, M, X, R⁷, R⁹ and R¹⁷ are as defined above and herein.

In certain embodiments, the present disclosure provides a metal complexof the formula (I-ll):

wherein M, X, R⁷ and R⁹ are as defined above and herein.

In certain embodiments, the present disclosure provides a metal complexof the formula (I-mm):

wherein M, X, Ring A, R³, R⁷ and R⁹ are as defined above and herein.

In certain embodiments, the present disclosure provides a metal complexof the formula (I-nn):

wherein M, X, Ring A, R¹, R², R³, R⁷ and R⁹ are as defined above andherein.

In certain embodiments, the present disclosure provides a metal complexof the formula (I-oo):

wherein M, X, R⁷, R⁹, R^(4A), R^(4B), R^(5A), R^(5B), and R^(6A), R^(6B)are as defined above and herein.

III. Exemplary Metal Complexes

In certain embodiments, the metal complex is selected from any one ofthe following, wherein X is absent or is a nucleophilic ligand:

In certain embodiments, the metal complex is selected from any one ofthe following, wherein X is absent or is a nucleophilic ligand:

In certain embodiments, the metal complex has the following structure,wherein X is absent or is a nucleophilic ligand:

In certain embodiments, the metal complex has the following structure,wherein X is absent or is a nucleophilic ligand:

In certain embodiments, the metal complex has the following structure,wherein X is absent or is a nucleophilic ligand:

In certain embodiments, the metal complex has the following structure,wherein X is absent or is a nucleophilic ligand:

In certain embodiments, the metal complex has the following structure,wherein X is absent or is a nucleophilic ligand:

In certain embodiments, X is absent.

In certain embodiments, X is —O(C═O)C₆F₅ (i.e., —OBzF₅). In certainembodiments, X is —OC(═O)CH₃. In certain embodiments, X is —OC(═O)CF₃.In certain embodiments, X is —NC. In certain embodiments, X is —Cl. Incertain embodiments, X is —Br. In certain embodiments, X is N₃.

In certain embodiments, the metal complex is a cobalt (Co) complexselected from any of the following structures:

In certain embodiments, the metal complex is a cobalt (Co) complexselected from any of the following structures:

In certain embodiments, the metal complex is a cobalt (Co) complexhaving the following structure:

In certain embodiments, the metal complex is a cobalt (Co) complexhaving the following structure:

In certain embodiments, the metal complex is a cobalt (Co) complexhaving the following structure:

In certain embodiments, the metal complex is a cobalt (Co) complexhaving the following structure:

In certain embodiments, the metal complex is a cobalt (Co) complexhaving the following structure:

IV. Methods of Making Poly(Ethylene Carbonate) Polymers

The present disclosure also provides methods of making variouspoly(ethylene carbonate) polymers. As used herein, poly(ethylenecarbonate) polymers are provided via polymerization of ethylene oxide(EO) and carbon dioxide (CO₂) in the presence of a metal complex, andencompass encompasses poly(ethylene carbonate) (PEC), as well aspolymers which comprise poly(ethylene carbonate), such as, for example,polyethylene oxide-co-polyethylene carbonate.

For example, in one aspect, the present disclosure provide a method ofsynthesizing a poly(ethylene carbonate) polymer, wherein the polymer ismade up of Y, and optionally Z, and wherein the percentage of Y isgreater than the percentage of Z,

the method comprising reacting ethylene oxide and carbon dioxide in thepresence of a metal complex.

In certain embodiments, the polymer has greater than about 85 percent ofY. In certain embodiments, the polymer has greater than about 90% of Y.In certain embodiments, the polymer has greater than about 95% of Y. Incertain embodiments, the polymer has greater than about 99% of Y. Incertain embodiments, the polymer is substantially all Y and issubstantially free of Z.

In certain embodiments, the polymer is an alternating polymer ofethylene oxide and carbon dioxide (e.g., with regular alternating unitsof ethylene oxide and carbon dioxide).

For example, wherein the polymer is substantially all Y and issubstantially free of Z, the polymer an alternating polymer of theformula:

wherein P is an integer of between about 10 and about 15,000, inclusive,and

each F and G are, independently, a suitable terminating group.

In certain embodiments, F is hydrogen. In certain embodiments F is ahydroxyl-protecting group. In certain embodiments F is an acyl group. Incertain embodiments F is a silyl group. In certain embodiments, G is X,where X is as described above. In certain embodiments, G is a hydroxylgroup.

In certain embodiments, P is an integer of between about 10,000 to about15,000, inclusive. In certain embodiments, P is an integer of betweenabout 12,000 to about 15,000, inclusive.

In certain embodiments, the metal complex is a zinc, cobalt, chromium,aluminum, titanium, ruthenium or manganese complex. In certainembodiments, the metal complex is an aluminum complex. In certainembodiments, the metal complex is a chromium complex. In certainembodiments, the complex metal is zinc complex. In certain embodiments,the metal complex is a titanium complex. In certain embodiments, themetal complex is a ruthenium complex. In certain embodiments, the metalcomplex is a manganese complex. In certain embodiments, the metalcomplex is cobalt complex. In certain embodiments, wherein the metalcomplex is a cobalt complex, the cobalt metal has a valency of +3 (i.e.,Co(III)).

In certain embodiments, the metal complex is any of the above describedmetal complexes of the formula (I), or subsets thereof.

In another aspect, the present disclosure provides a method ofsynthesizing a poly(ethylene carbonate) polymer, the method comprisingthe step of reacting ethylene oxide with carbon dioxide in the presenceof a cobalt complex of any of the above described metal complexes of theformula (I), or a subset thereof, wherein M is cobalt.

Reaction Conditions

In certain embodiments, any of the above methods further comprise aco-catalyst.

In certain embodiments, the co-catalyst is a Lewis base. Exemplary Lewisbases include, but are not limited to: N-methylimidazole (N-MeIm),dimethylaminopyridine (DMAP), 1,4-diazabicyclo[2.2.2]octane (DABCO),triethyl amine, and diisopropyl ethyl amine.

In certain embodiments, the co-catalyst is a salt. In certainembodiments, the co-catalyst is an ammonium salt, a phosphonium salt oran arsonium salt. In certain embodiments, the co-catalyst is an ammoniumsalt. Exemplary ammonium salts include, but are not limited to:(n-Bu)₄NCl, (n-Bu)₄NBr, (n-Bu)₄NN₃, [PPN]Cl, [PPN]Br, and [PPN]N₃,Ph₃PCPh₃]Cl [PPN]O(C═O)R^(c) (PPN=Bis(triphenylphosphoranylidene)ammonium)). In certain embodiments, the co-catalyst is a phosphoniumsalt. In certain embodiments, the co-catalyst is an arsonium salt.

In certain embodiments, the co-catalyst is the ammonium saltbis(triphenylphosphoranylidene)ammonium chloride ([PPN]Cl).

In certain embodiments, the anion of the salt co-catalyst has the samestructure as the ligand X of the above described metal complexes of theformula (I), or subsets thereof, wherein X is a nucleophilic ligand. Forexample, in certain embodiments, the co-catalyst is ([PPN]X) or(n-Bu)₄NX.

In certain embodiments, any of the above methods comprise a ratio ofabout 500:1 to about 500,000:1 of ethylene oxide to metal complex. Incertain embodiments, any of the above methods comprise a ratio of about500:1 to about 100,000:1 of ethylene oxide to metal complex. In certainembodiments, any of the above methods comprise a ratio of about 500:1 toabout 50,000:1 of ethylene oxide to metal complex. In certainembodiments, any of the above methods comprise a ratio of about 500:1 toabout 5,000:1 of ethylene oxide to metal complex. In certainembodiments, any of the above methods comprise a ratio of about 500:1 toabout 1,000:1 of ethylene oxide to metal complex.

In certain embodiments, any of the above methods comprise ethylene oxidepresent in amounts between about 0.5 M to about 20 M. In certainembodiments, ethylene oxide is present in amounts between about 0.5 M toabout 2 M. In certain embodiments, ethylene oxide is present in amountsbetween about 2 M to about 5 M. In certain embodiments, ethylene oxideis present in amounts between about 5 M to about 20 M. In certainembodiments, ethylene oxide is present in an amount of about 20 M. Incertain embodiments, liquid ethylene oxide comprises the reactionsolvent.

In certain embodiments, CO₂ is present at a pressure of between about 30psi to about 800 psi. In certain embodiments, CO₂ is present at apressure of between about 30 psi to about 500 psi. In certainembodiments, CO₂ is present at a pressure of between about 30 psi toabout 400 psi. In certain embodiments, CO₂ is present at a pressure ofbetween about 30 psi to about 300 psi. In certain embodiments, CO₂ ispresent at a pressure of between about 30 psi to about 200 psi. Incertain embodiments, CO₂ is present at a pressure of between about 30psi to about 100 psi. In certain embodiments, CO₂ is present at apressure of between about 30 psi to about 80 psi. In certainembodiments, CO₂ is present at a pressure of about 30 psi. In certainembodiments, CO₂ is present at a pressure of about 50 psi. In certainembodiments, CO₂ is present at a pressure of about 100 psi. In certainembodiments, the CO₂ is supercritical.

In certain embodiments, any of the above methods comprise the reactionto be conducted at a temperature of between about 0° C. to about 100° C.In certain embodiments, the reaction is conducted at a temperature ofbetween about 23° C. to about 100° C. In certain embodiments, thereaction to be conducted at a temperature of between about 23° C. toabout 80° C. In certain embodiments, the reaction to be conducted at atemperature of between about 23° C. to about 50° C. In certainembodiments, the reaction to be conducted at a temperature of about 23°C.

In certain embodiments, the reaction step of any of the above methodsdoes not further comprise a solvent.

However, in certain embodiments, the reaction step of any of the abovemethods does further comprise one or more solvents. In certainembodiments, the solvent is an organic solvent. In certain embodiments,the solvent is an organic ether. In certain embodiments, the solvent isan aromatic hydrocarbon. In certain embodiments the solvent is a ketone.

In certain embodiments suitable solvents include, but are not limitedto: Methylene Chloride, Chloroform, 1,2-Dichloroethane, PropyleneCarbonate, Acetonitrile, Dimethylformamide, N-Methyl-2-pyrrolidone,Dimethyl Sulfoxide, Nitromethane, Caprolactone, 1,4-Dioxane, and1,3-Dioxane.

In certain other embodiments, suitable solvents include, but are notlimited to: Methyl Acetate, Ethyl Acetate, Acetone, Methyl Ethyl Ketone,Propylene Oxide, Tretrahydrofuran, Monoglyme Triglyme, Propionitrile,1-Nitropropane, Cyclohexanone.

In certain embodiments, the reaction step of any of the above methodsproduces ethylene carbonate (EC) as a by-product in amounts of less thanabout 20%. In certain embodiments, ethylene carbonate (EC) is producedas a by-product in amounts of less than about 15%. In certainembodiments, ethylene carbonate (EC) is produced as a by-product inamounts of less than about 10%. In certain embodiments, ethylenecarbonate (EC) is produced as a by-product in amounts of less than about5%. In certain embodiments, ethylene carbonate (EC) is produced as aby-product in amounts of less than about 1%. In certain embodiments, thereaction does not produce any detectable by-products (e.g., asdetectable by ¹H-NMR and/or liquid chromatography (LC)).

Tapered and Block Co-Polymers

As is understood from the above, the poly(ethylene carbonate) polymer isa co-polymer of units “Y” and “Z”:

In certain embodiments, the poly(ethylene carbonate) polymer is atapered co-polymer of units Y and Z (e.g., wherein the incorporation ofZ increases or decreases along the length of a given polymer chain.):

In certain embodiments, the poly(ethylene carbonate) polymer is a blockco-polymer of homopolymer units of Y and Z; the union of the homopolymersubunits may require an intermediate non-repeating subunit, known as ajunction block. Block copolymers with two or three distinct blocks arecalled diblock copolymers and triblock copolymers, respectively.

In certain embodiments, the tapered or block co-polymer of poly(ethylenecarbonate) is of the formula:

wherein each instance of P and Q are, independently, an integer ofbetween about 10 to about 10,000, inclusive, and wherein R is an integerranging from about 1 to about 20,

each F and G are, independently, suitable terminating groups, asdescribed above and herein.

For example, in certain embodiments, the present disclosure provides amethod of making a poly(ethylene carbonate) block co-polymer, comprisingthe steps of (i) providing a polyethylene oxide (PEO) polymer, and (ii)reacting the polyethylene oxide polymer with ethylene oxide and carbondioxide in the presence of a metal complex. In certain embodiments, themetal complex is a metal complex of formula (I), or any subset thereof.

In certain embodiments, the polyethylene oxide polymer of step (i) isprovided by reacting ethylene oxide in the presence of a metal complex.In certain embodiments, the metal complex is a metal complex of formula(I), or any subset thereof.

In certain embodiments block copolymer compositions may be produced byvarying or removing the CO₂ pressure during part of the polymerizationprocess. When the CO2 pressure is low or non-existent, the catalyst willproduce polymer having a higher degree of ether linkages than when theCO2 pressure is high. Thus, in certain embodiments of the presentdisclosure the polymerization may be initiated with any of the metalcomplexes described above at a relatively high CO₂ pressure (forexample, higher than 100 psi, higher than about 200 psi, or higher thanabout 400 psi). These conditions will produce polymer having apredominance of carbonate linkages. After a length of time, the CO₂pressure is lowered (for example to less than 100 psi, less than 50 psi,or to atmospheric pressure) or is removed completely. These conditionsresult in new block with more ether bonds being incorporated into thegrowing polymer chains. The above described process can optionally berepeated one or more times to build diblock, triblock or multiblockpolymers. Additionally, several different CO₂ pressure levels can beused in the process to produce polymers with several different blocktypes. In certain embodiments, the CO₂ pressure is initially low and isthen increased. In certain other embodiments the CO₂ pressure is variedperiodically. In certain other embodiments, the CO₂ pressure is variedsmoothly over time to form tapered polyether co polycarbonate polymercompositions or blocks with a tapered copolymeric structure.

EXEMPLIFICATION Example 1 Highly Active Cobalt Catalysts for AlternatingCopolymerization of Ethylene Oxide and Carbon Dioxide

The inventors have recently found that (salcy)CoOBzF₅(salcy=N,N′-bis(3,5-di-tert-butylsalicylidene)-1,2-diaminocyclohexane;OBzF₅=pentafluorobenzoate; 1) efficiently copolymerizes cyclohexeneoxide (CHO) or propylene oxide (PO) with CO₂. However, there has been noreport using 1 for the copolymerization of EO and CO₂ to make PEC.Herein is reported the development of highly active Co(salcy) catalystsfor the copolymerization of EO/CO₂ under low CO₂ pressure to producecopolymers with high carbonate percentages.

The recent success using 1 with bis(triphenylphosphoranylidene)ammoniumchloride ([PPN]Cl) to copolymerize PO and CO₂ led us to investigate thiscatalytic system for the copolymerization of EO and CO₂ (Scheme 1 andTable 2) (see (a) Moore, D. R.; Cheng, M.; Lobkovsky, E. B.; Coates, G.W. Angew. Chem. Int. Ed. 2002, 41, 2599-2602. (b) Cheng, M.; Moore, D.R.; Reczek, J. J.; Chamberian, B. M.; Lobkovsky, E. B.; Coates, G. W. J.Am. Chem. Soc. 2001, 123, 8738-8749. (c) Cheng, M.; Lobkovsky, E. B.;Coates, G. W. J. Am. Chem. Soc. 1998, 120, 11018-11019. (d) Allen, S.D.; Moore, D. R.; Lobkovsky, E. B.; Coates, G. W. J. Am. Chem. Soc.2002, 124, 14284-14285. (e) Qin, Z. Q.; Thomas, C. M.; Lee, S.; Coates,G. W. Angew. Chem. Int. Ed. 2003, 42, 5484-5487. (f) Cohen, C. T.; Chu,T.; Coates, G. W. J. Am. Chem. Soc. 2005, 127, 10869-10878. (g) Cohen,C. T.; Coates, G. W. J. Polym. Sci., Part A: Polym. Chem. 2006, 44,5182-5191).

TABLE 2 Co Catalyst R⁷ R⁹ 1 t-Bu t-Bu 2 —C(Me)(Et)₂ t-Bu 3 —C(Et)₃ t-Bu4 —C(Me)₂CH₂C(Me)₃ t-Bu 5 —C(Et)₃ —CH₃ 6 —C(Et)₃ i—Pr 7 —CH₃ —C(Et)₃ 8t-Amyl (—CH₂C(CH₃) t-Amyl (—CH₂C(CH₃) 9 Cumyl (—C(CH₃)₂Ph) Cumyl(—C(CH₃)₂Ph) —OBzF₅O = —O(C═O)C₆F₅

Co Catalysts

Reacting 1/[PPN]Cl with EO under 100 psi CO₂ at 22° C. produced a veryviscous solution after just 1 hour, which suggested that 1/[PPN]Cl wasactive for EO/CO₂ copolymerization. Further analysis of the productrevealed poly(EO-co-EC) had been synthesized (entry 1, Table 3).

The ¹H NMR spectrum of the polymer produced by 1/[PPN]Cl is shown inFIG. 1A. In addition to the expected polycarbonate peak (a), shifts werealso observed which correspond to ether linkages (b, c, d), indicatingthat the copolymerization under these conditions is not perfectlyalternating. Ether incorporation is problematic because it negativelyaffects the gas barrier properties. Despite many changes in the reactionconditions, we were unable to completely suppress ether incorporationusing catalyst 1.

TABLE 3 Experimental Conditions and Results of Copolymerization of EOand CO₂ ^(a) carbon- cata- [Co] yield^(b) TOF^(c) ate^(d) PEC: EC^(e)M_(n) ^(f) M_(w)/ entry lyst (mM) (%) (h⁻¹) (%) (% PEC) (g/mol) M_(n)^(f)  1 1 10 47 940 67 83 25,900 1.6  2^(g) 1 10 21 830 85 99 14,100 1.4 3 1 5.0 21 830 89 97 36,700 1.4  4^(h) 1 2.0 16 520 93 >99 34,800 1.5 5^(i) 1 5.0 19 760 90 99 24,400 1.3  6^(j) 1 5.0 13 510 89 99 15,7001.3  7^(k) 1 10 26 170 84 >99 22,800 1.2  8^(l) 1 5.0 46 610 76 9929,800 1.5  9 2 10 41 820 99 93 28,900 1.3 10 3 10 27 540 >99 95 32,4001.3 11 4 10 20 400 >99 95 27,100 1.4 12 5 10 13 250 >99 68 28,100 1.4 136 10 26 530 >99 86 26,500 1.3 14 7 10 34 680 98 91 26,100 1.4 15 8 10 45910 97 94 33,700 1.4 16 9 10 22 430 >99 80 26,000 1.4 17 10 10 27 540 9281 29,400 1.5 ^(a)Polymerizations run in neat ethylene oxide (EO); [EO]₀= 20M; [Co]₀ = [[PPN]Cl]₀; with 100 psi of CO₂ at 22° C. for 1 h.^(b)Determined by crude products mass assuming that both PEC and EC arepresent. ^(c)Turnover frequency = mol PEC/mol Co · h. ^(d)Determined by¹H NMR spectroscopy of the purified copolymer. ^(e)Determined by ¹H NMRspectroscopy of PEC and EC of the crude product. ^(f)Determined by gelpermeation chromatography calibrated with PMMA standards in DMF. ^(g)30min. ^(h)3 h. ^(i)P_(CO) ₂ = 80 psi. ^(j)P_(CO) ₂ = 50 psi. ^(k)0° C.for 3 h. ^(l)[EO]₀ = 10M in 1,4-dioxane for 1.5 h.

In order to achieve a perfectly alternating copolymerization, thecatalyst structure was optimized by varying ligand substituents. Severalcatalysts were prepared by changing R⁷ and/or R⁹ (Scheme 1), andscreened for EO/CO₂ copolymerization (Table 3). Catalysts 1-10 wereactive for the copolymerization and their activities were influenced bythe substituents R⁷ and R⁹. With tert-butyl groups at R⁷ and R⁹ (1), thecopolymerization proceeded rapidly to give 47% EO conversion in 1 hourwith a high turnover frequency (TOF) (entry 1). After 1 hour, thecopolymerization solution was very viscous, preventing the dissolutionof CO₂ and effectively stopping the polymerization. In addition, backbiting occurred to produce 17% ethylene carbonate (EC) (entry 1).Reducing the reaction time to 30 min kept viscosity low, thus reducedback biting and increased carbonate percentage (entry 2). Compared with1, 2 bearing bulkier substituents at R¹ gave a copolymer with highercarbonate percentage, although the catalytic activity slightly decreased(entry 9). This suggested the bulkiness of the R⁷ substituentsignificantly impacts carbonate percentage. Complexes 3 and 4 producednearly perfect alternating PEC (entry 10 and 11). The carbonate contentfollowed the trend 1<2<3<4 and the activity trend was 1>2>3>4. Thisdemonstrates that carbonate percentage increases with steric bulk whileactivity decreases.

The effects of changing R⁹ were also examined. Catalyst 5, bearing a Megroup, afforded the slowest polymerization resulting a TOF of 250 h⁻¹,however, the resulting copolymer exhibited very high carbonatepercentage, 99.1% (entry 12). Complex 6 where R⁹=i-Pr showed similarcatalytic activity and similar carbonate percentage as complex 3 (entry13). This observation suggests that the substituent R⁹ does notsignificantly influence the carbonate percentage but does influence therate.

Complex 7, which has a small substituent at R⁷ and a bulky substituentat R⁹, was expected to show high activity and low carbonate percentagein the resulting copolymer. The catalytic activity was relatively high,however, to our surprise, 98% carbonate percentage was obtainedregardless of the small substituent at R⁷. This result suggests that thelarger substituents for R⁷ and R⁹ improve the activity and the carbonatepercentage.

Complexes 8 and 9 were rapidly prepared from commercially availabledisubstituted phenols and were also evaluated for the copolymerization.Catalyst 8 exhibited a high TOF of 910 h⁻¹ comparable to 1 and gavehigher carbonate percentage of 96.8% (entry 15). Catalyst 9 gave a TOFof 430 n⁻¹, which is slower than 1 and 8. However, 9 gave very highcarbonate percentage of 99.1% (entry 16). Among these three catalysts,the least sterically hindered compound 1, gave the highest activity andthe lowest carbonate percentage, while the most sterically hinderedcompound 9, gave the lowest activity but the highest carbonatepercentage. This mirrors the trend observed with compounds 1-4.

We also screened 10, which is identical to 1, but has a phenyl backbonein place of the cyclohexyl. A similar version of this catalyst, with anacetate initiator, induces the stereoselective homopolymerization of POto give perfectly isotactic polypropylene oxide). The catalytic activityand the carbonate linkage content were 540 h⁻¹ and 92.1%, respectively,not as high active as with 1, although the structure is very similar tothat of 1 (entry 17).

Reducing the concentration of 1 caused a decrease in the catalyticactivity but an increase of the carbonate linkage (entry 3 and 4). Thisresult suggests that the insertion rates of EO to alkoxide and carbonatetermini in the copolymer depend on the Co concentration, and the EOinsertion may involve a bimetallic mechanism of the catalyst.

Copolymerizations were also performed by filling CO₂ into the solutionof EO, Co catalyst, and cocatalyst (PPNCl) under 30-400 psi at roomtemperature to give poly(ethylene carbonate) (PEC). The catalysticactivities were higher than those of other catalyst to give ca. 100g-polymer/g-catalyst·h (for catalyst 1). The catalytic activities werecompared among the catalysts 2, 8, 9 (Table 4). It proved that the morebulky substituent in the catalyst, the less active.

TABLE 4 Comparison of Co catalyst^(a)) Activity, g-polymer/g- CarbonateCatalyst Yield, % TOF, h⁻¹ cat · h Linkage, % 1 44.3 886 95.7 66.0 842.2 844 85.3 96.7 9 21.5 430 35.7 99.1 2 38.1 762 77.0 98.9 ^(a))EO =100 mmol, Co cat = 0.050 mmol, PPNCl = 0.050 mmol, P_(CO2) = 100 psi,Polymerization time = 1 h.

The effect of the catalyst concentration (of catalyst 1) to thecatalytic activity was also investigated. As shown in Table 5, thecatalytic activity increased with the catalyst 1 concentration.

TABLE 5 Effect of Catalyst Concentration^(a)) Activity, [Co 1]₀,Reaction Yield, g-polymer/ Carbonate mM Time, h % TOF, h⁻¹ g-cat · hLinkage, % 1.0 2 3.1 310 32.6 93.2 5.0 2.5 37.7 602 64.4 85.2 9.1 1 31.9708 74.8 71.6 10 1 44.3 886 95.7 66.0 ^(a))[EO]₀ = 20 M (bulk), [Co]₀ =[PPNCl]₀, P_(CO2) = 100 psi.

Table 5 shows the effect of CO₂ pressure to catalytic activity ofcatalyst 1. The activity increased with the pressure at low pressure.However, it had a maximum about 200 psi.

TABLE 6 Effect of CO₂ Pressure^(a)) Activity, Reaction g-polymer/Carbonate P_(CO2) Time, h Yield, % TOF, h⁻¹ g-cat · h Linkage, % 50 44.1 203 19.9 96.0 100 2 3.1 310 32.6 93.2 200 3 9.1 606 62.9 74.4 400 22.8 278 29.2 64.9 ^(a))[EO]₀ = 20 M (bulk), [Co 1]₀ = [PPNCl]₀ = 1.0 mM.

From ¹H NMR analysis, the obtained polymers mainly consist of carbonatelinkage but have some amount of ether linkage, which depended on thereaction conditions (catalyst concentration, CO₂ pressure, and reactiontemperature) and substituents of the catalyst (see FIGS. 1 and 2). Themost active catalyst 1 had the least carbonate linkage and the leastactive catalyst 2 had the highest carbonate linkage. Especially, thecatalyst 2 produced almost perfect PEC. The effect of the catalystconcentration to the carbonate linkage were also shown in Table 5. Itshowed that the carbonate linkage increased by decreasing the catalystconcentration. The CO₂ pressure also affected the carbonate linkage.Opposite to expected, the carbonate linkage decreased by increasing thepressure as shown in Table 6.

Catalyst 15 has also been found to be effective to provide apoly(ethylene carbonate-co-ethylene oxide) polymer.

EO:CO:PPNCl=2000:1:1; PCO₂=100 psi; 3 hr; 14% yield of polymer; TOF=92h⁻¹; carbonate linkage 96%; PEC:EC=93:7.

In conclusion, we have reported the first examples of Co-catalyzedEO/CO₂ copolymerization. The polymerizations were very fast even underrelatively low pressure. The obtained copolymer consists not only ofcarbonate linkages but also ether linkages which indicates both EO/CO₂alternating copolymerization and EO homopolymerization are occurringduring the copolymerization. The ether content can be decreased throughthe catalyst design. Catalyst 3 gave a high catalytic activity and acopolymer with the greatest carbonate content, which is almost aperfectly alternating copolymer.

Example 2 Polymerization of Ethylene Oxide (PEO)

(Salcy)CoOBzF₅ induced ethylene oxide (EO) polymerization in thepresence of PPNCl. The activity was strongly depended on the PPNCl/Coratio (see Table 7 and FIG. 3).

TABLE 7 Effect of [PPNCl]/[Co] Product [PPNCl]/[Co] Mass, g Yield, %TOF, h⁻¹ 0.2 0.1535 3.5 836 0.3 0.3252 7.4 1777 0.5 0.2065 4.7 1125 0.70.1917 4.4 1044 1 0.1030 2.3 561 [EO]₀ = 20 M, [Co]₀ = 5.0 mM, [PPNCl]₀= 1.0-5.0 mM, rt 10 min.

Example 3 Synthesis of Block Copolymer of PEO-b-PEC

The one-pot PEO-b-PEC synthesis was then examined. PEO was polymerizedin a glass autoclave first, and then the reaction solution waspressurized with CO₂ to undergo EO/CO₂ copolymerization. This polymerconsists of hard segment (PEO)/soft segment (PEC), and is thusconsidered to have a new function (see FIGS. 4A-4B depicting the TGA andDSC analyses of PEO-b-PEC).

Other Embodiments

The foregoing has been a description of certain non-limiting preferredembodiments. Those of ordinary skill in the art will appreciate thatvarious changes and modifications to this description may be madewithout departing from the spirit or scope of the present disclosure, asdefined in the following claims.

1-140. (canceled)
 141. A metal complex of the formula:

wherein: M is a metal selected from zinc, cobalt, chromium, aluminum,titanium, ruthenium or manganese; X is absent or is a nucleophilicligand; ring A forms an optionally substituted 5- to 6-membered ring;each R³ is, independently, selected from hydrogen, halogen, optionallysubstituted aliphatic, optionally substituted heteroaliphatic,optionally substituted aryl, and optionally substituted heteroaryl; R⁷and R⁹ are, independently, selected from hydrogen, optionallysubstituted aliphatic, optionally substituted heteroaliphatic,optionally substituted aryl, optionally substituted heteroaryl; andcharacterized in that R⁹ has a molecular volume at least two timesgreater than the molecular volume of R⁷.
 142. The metal complex of claim141, wherein the molecular volume of R⁹ is at least 3 times larger thanthe molecular volume of R⁷.
 143. The metal complex of claim 141, whereinan A-value of R⁹ is at least two times larger than an A-value for R⁷.144. The metal complex of claim 141, wherein the A-value of R⁹ isgreater than about 2.5 kcal/mol.
 145. The metal complex of claim 141,wherein the A-value of R⁹ is greater than about 3 kcal/mol.
 146. Themetal complex of claim 141, wherein the A-value of R⁹ is greater thanabout 4 kcal/mol.
 147. The metal complex of claim 141, wherein each R³is hydrogen.
 148. The metal complex of claim 141, wherein the complex isof the formula:


149. The metal complex of claim 141, wherein M is cobalt or chromium.150. The metal complex of claim 141, wherein M is cobalt (III).
 151. Amethod of synthesizing a poly(ethylene carbonate) polymer, the methodcomprising reacting ethylene oxide and carbon dioxide in the presence ofa metal complex of the formula:

wherein: M is a metal selected from zinc, cobalt, chromium, aluminum,titanium, ruthenium or manganese; X is absent or is a nucleophilicligand; ring A forms an optionally substituted 5- to 6-membered ring;each R³ is, independently, selected from hydrogen, halogen, optionallysubstituted aliphatic, optionally substituted heteroaliphatic,optionally substituted aryl, and optionally substituted heteroaryl; R⁷and R⁹ are, independently, selected from hydrogen, optionallysubstituted aliphatic, optionally substituted heteroaliphatic,optionally substituted aryl, optionally substituted heteroaryl; andcharacterized in that R⁹ has a molecular volume at least two timesgreater than the molecular volume of R⁷.
 152. The method of claim 151,wherein the molecular volume of R⁹ is at least 3 times larger than themolecular volume of R⁷.
 153. The method of claim 151, wherein an A-valueof R⁹ is at least two times larger than an A-value for R⁷.
 154. Themethod of claim 151, wherein the A-value of R⁹ is greater than about 2.5kcal/mol.
 155. The method of claim 151, wherein the A-value of R⁹ isgreater than about 3 kcal/mol.
 156. The method of claim 151, wherein theA-value of R⁹ is greater than about 4 kcal/mol.
 157. The method of claim151, wherein each R³ is hydrogen.
 158. The method of claim 151, whereinthe complex is of the formula:


159. The method of claim 151, wherein M is cobalt or chromium.
 160. Themethod of claim 151, wherein M is cobalt (III).